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STANDARD 

American Cyclopedia of Steam Engineering 

A Treatise on the Care and Management 
of Steam Engines, Boilers and Dynamos 



Including Instructions for an Efficient Management of all Classes of 
Steam Engines, Boiler Operation, Care of the Boiler, including Wash- 
ing Out, How to Fire a Boiler, Etc. Valves and Valve Setting, includ- 
ing Correct Adjustment of Single Valve and Corliss Engines. Mechani- 
cal Stokers and the Principle Involved in the Action of Automatic 
Stokers. Steam Turbine Engines, their Construction and Operations, 
the Fundamental Principles of the Steam Turbine, Types of Steam 
Turbine, Speed Regulation and Efficiency. Refrigeration, Pumps and 
Ail mpressors. Electricity for Engineers, Including Construction 
and Operation of Dynamos, Motors, Lamps, Storage Batteries, Etc. 
A Complete Engineers' Catechism, Embodying Questions and Answers 
Necessary to Pass Successful Examinations for Licenses for Station- 
ary and Marine Engineer. Mechanical and Machine Drawing, with 
Plain and Simple Instructions. 



FULLY ILLUSTRATED 



By CALVIN F. SWINGLE AND OTHERS 



Special Exclusive Edition 
Printed by 

FREDERICK J. DRAKE & CO. 

EXPRESSLY FOR 

SEARS, ROEBUCK & COMPANY 
CHICAGO, ILL. 

1'915 



TJa7€ 
Sss 



Copyright 1915 

BY 

FEEDERICK J. DRAKE & CO. 



Copyright 1913 

BY 

FREDERICK J. DRAKE & CO. 



Copyright 1912 

BY 

FREDERICK J. DRAKE 



FEB 26 1915 

©CI,.A391919 



LIST OF ILLUSTRATIONS 



American Thompson indicator, 

176. 

Amsler^s polar planimeter, 263. 
Ashcroft steam gauge, 36. 

Baragwanath closed heater, 53. 

Baragwanath open heater, 55, 

Babcock and Wilcox water 
tube boiler, 16. 

Berryman closed heater, 57. 

Baragwanath siphon conden- 
ser, 272. 

Coffin averager or planimeter, 

261. 
Crosby indicator, sectional view, 

170. 
Crosby indicator, with reducing 

wheel, 183. 
Cross compound Allis-Chalmers 

engine, 266. 
Center oiler for crank pin, 279. 

Davis belt-driven feed pump, 48. 
Differential valve for Davis 

pump, 47-49. 
Detroit lubricator, 277. 

Green's fuel economizer — under 
construction, 94. 

Hamilton Corliss engine-— cross 

compound, 268. 
Horizontal boiler setting, 12. 
Heine water tube boiler, 14. 
Hot water thermometer, 59. 



PART I STEAM ENGINEERING 

Inside view of pop valve, 41, 



Knowles jet condenser, 269 

Lahman shaking grate, 67. , 

Martin rocking grate, 68. 
Marsh steam pump, 50. 
Metropolitan injector, 52. 
McClave shaking grate, 33-35 

Pop safety valve, 40. 
Pickering governor, 276. 
Penberthy injector — sectional 
view, 285. 

Schaefer and Budenberg steam 

gauge, 38. 
Sectional view of pressure gauge, 

37. 
Sectional view of Corliss cylinder 

and valve chests, 158. 
Shaft governor, 281. 

Tandem compound Buckeye 

engine, 267. 
U. S. Automatic injector, 51. 
Wickes vertical water tube 

boiler, 13. 
Worthington duplex feed pump, 

49. 
Worthington surface condenser, 

271. 



INDEX 



PART I — STEAM ENGINEERING 



Absolute pressure, 190. 
Absolute back pressure, 191. 
Absolute zero, 193. 
Action of slide valve, 134-139. 
Adiabatic curve, 194-252-254. 
Adjustable cut-off, 145-203. 
Admission, 1C8. 
Admission line, 208. 
Adjustment of governor, 164- 
165. 

Air — 

Composition of, 91. 

Cubic feet per lb. of coal 

burned, 70-93. 
Leaks in boiler settings, 33-34. 
How to admit to furnace, 

70-71. 

Angular Advance — 

Necessity of, 136. 

Effect of decreasing, 144. 

Effect of increasing, 148-149 

Definition of, 201. 
Analysis of coal, 92. 
Apparatus for making tests, 

118-120. 

Of circles, 204-205. 

Of fire box, 61. 

Of grate surface, 121. 

Of Keating surfaoe, 61. 

Of safety valve, 39. 

Of segments, 22. 

Sectional of braces, 21-22-23. 

Ash— 

Dry, 123. 

Removal of, 29-121 

Weight of, 127. 
Atoms, 106-107, 
Atmospheric line, 186. 
Automatic stoker, 94. 
Automatic cut-off, 202. 



Back pressure, 190. 
Blow-off — 

Pipes, 45-47. 

Cock, 46. 

Surface, 47. 
Boiler — 

Air leaks in brick work, 34. 

Back arches, 29-31-34. 

Bridge Walls, 28. 

Bracing, rules for, 22-23-24, 

Bursting pressure, 18. 

Cleaning, 71-73.. 

Combustion chamber, 29. 

Contraction of plates, 43. 

Expansion of plates, 44. 

Factor of safety, 21. 

Force tending to rupture, 19, 

Flue cvHndrical, 11.* 

Grate surface, 32-33. 

Horse power of, 131. 

How to prevent alternate ex- 
pansion and contraction, 
72-73. 

Incrustation, 104. 

Insulation, 33-34. 

Inspection, 73-74. 

Operation of, 66. 

Plain cylinder, 11. 

Return tubular, 12. 

Rivets, 15-16. 

Settings, 27. 

Set in battery, 28-122. . . . 

Shell material, 14-15. 

Types of , 11. 

Tubes, renewing of, 74. 

Water tube, i3. 

What causes alternate ex- 
pansion and contraction. 73, 
Boyle's law, 194. 
Box valve, 157. 
Brumbo pulley, 181. 
British thermal unit, 98-99. 
Buck stays, 31-32. 



INDEX 



Calorimeter, 124. 

Chimney draft, 124. 

Circulating system, 47. 

Cleaning fires, 67. 

Cleaning flues, 71-72. 

Clearance, 193-236-245-246. 

Combustion, 91-94. 

Coal- 
Analysis of, 92. 
Moisture in, 124. 

Composition of matter, 106. 

Connecting steam gauge, 38. 

Connecting boiler to main head- 
er, 75-76. 

Corliss valves, 158-163. 

Corliss valve gear, 158-160. 

Condenser pressure, 191. 

Counter pressure, 260. 

Compression, 194-202-236-238. 

Condenser — 
Jet, 270. 
Surface, 270. 
Siphon, 271. 

Water required per H. P. per 
hour, 274-276. 

Curves — 

Adiabatic, 194-252-254. 
Compression, 236-238. 
Expansion, 194. 
Isothermal, 194-246-251. 
Theoretical expansion, 246- 
251. 

Cut-off- 
Automatic, 202. 
Adjustable, 203. 
At half stroke, 149. 
EquaUzing, 212-226. 
Fixed, 202. 
Of slide valve, 137-142. 

Cylinder condensation, 200. 

Dash pot, 162-165.' 
Diagrams — 

From Corliss centennial en- 
gine, 232-235. 

From Hamilton Corliss en- 
gine, 235-236. 

From Buckeye engine, 208- 
216-218-226-227. 

From Bates vertical Corliss 
engine, 209-212. 



Diagrams— 

From Bullock horizontal Cor- 
liss engine, 213-216. 
From Atlas riding cut off 

engine, 218. 
From cross compound con- 
densing engine, 219-220. 
From Fishkill Corliss con- 
densing engine, 222-224. 
From vertical slide valve en- 
gine, 224-225. 
Friction, 260. 

Showing lines and curves, 207. 
Domes — 

Purpose of, 43. 
Bracing, 24. 
Draft gauge, 125. 
Duplex Pump — 

How to set valves of, 81-82. 
How to operate with one 
water piston disabled, 82- 
83. 
Dynamics, 195. 

Economy in fuel, 51-57. 
Economizers, 94. 
Eccentric — 

Adjustment of, 156-161. 

Definition of, 200. 

Position, 138-139-201. 

Rod, length of, 153-154. 

Throw, 201. 
Efficiency test, 122. 
Efficiency of plant, 197. 
Energy in one pound of coal, 

102.* 
Engine — 

Corfiss, 158. 

Compound, 268. 

Compound, distribution of 
steam in cylinders, 221-222. 

Changing of speed, 287-288. 

Efficiency of, 196-197. 

Four valve, 157-159. 

How to place on center, 
150-153. 

Keying up, 281-282. 

Operation of, 266-288. 

Steam consumption of, 198- 
236-238-242. 

Single valve, 134. 



INDEX 



Equivalent evaporation, 127. 
Evaporation — 

Factor of, 128-129. 
Exhaust — 

Cramped, 225. 

Injector, 57-58. 

Heater, 53-54-55-57. 

Line, 208. 
Expansion curve, 194-208. 

Factor of safety, 20. 

Factor of evaporation, 128-129. 

Feed pipes, 43-45. 

Feed Pumps — 

Belt driven, 47. 

Best water valves for, 80. 

Double acting, 48. 

Selection of, 48-50. 

Setting steam valves of du- 
plex pump, 81-82. 
Peed Water — 

Heating by exhaust steam, 
283-285. 

Proper supply of, 74-75. 

Quantity required, 49-51. 

Temperature of, 43. 

What to do if supply is cut 
off, 75. 
Feed Water Heaters — 

Closed, 53. 

Capacity of, 56-57. 

Economy of, 52. 

Live steam, 58. y 

Open, 53. 
Fire tools, 68. 

Firing, proper method of, 69-71. 
Fire brick lining, 28-33. 
First law of thermo-dynamics, 

194. 
First law of motion, 194-195 
Fixed cut-off, 202. 
Foaming, 76. 
Formula — 

For ascertaining friction loss 
in water pipes, 87. 

For decreasing speed of en- 
gine, 288. 

For double riveting, 20. 

For efficiency of boiler, 130. 

For estimating quantity of 
condensing water, 274. 



Formula — 

For finding bursting pres- 
sure, 20. 
For finding heating surface, 

62-64. 
For increasing speed of en- 
gine, 287. 
For per cent, of saving by 
use of exhaust heater, 56. 
For single riveting, 21. 
Force, definition of, 195. 
Friction of water in pipes, 

86-88. 
Fusible plugs, 40-42. 
Furnace temperature, 93. 

Gauges — 

Draft, 125. 

Steam, connecting, 38-39-40. 

Vacuum, 192. 
Gauge pressure, 190. 
Generation of steam, 107. 
Governor — 

Throttling, 202-276. 

Automatic cut-off, 276. 

Isochronol, 202-281. 
Grate Surface — 

Length and width of, 32. 

Ratio of to heating surface, 33. 

Ratio of to safety valve area^ 
39-40. 

Square feet of, 121. 
Gridiron valve, 157. 

Hand firing, 95. 

Hand holes, reenforcing, 24. 

Heater — 

Closed, 53-57. 

Capacity of, 56. 

Live steam, 57. 

Open, 54-55. 

Economy of, 52. 
Heating Surface — 

Of horizontal boilers, 61. 

Of vertical fire box boilers, 61 
Heat — 

A form of energy, 96. 

External work of, 108., 

Internal work of, 108- 

Intensity of, 95. 

Latent, 102-103. 



INDEX 



Heat — 

Mechanical equivalent of, 99. 

Original source of, 97. 

Sensible, 99-101. 

Specific, 99. 

Theories regarding nature of 
95—96. 

Unit of, 98-99. 
High speed engines, 157. 
Hook rod, adjusting length of, 

160-161. 
Horizontal boiler setting, 12. 
Horse Power — 

Definition of, 102-193. 

Constant, 197-228-230. 

Indicated, 193. 

Net, 194. 
Hot water thermometer, 58-59. 
Hydraulics, 83-87. 
Hydrogen, 91. 
Hyperbolic logarithms, 188. 

Internally fired boilers, 23. 
Initial pressure, 190. 
Injector — 

Care of, 286. 

Exhaust, 285. 

Live steam, 286. 

Principles of, 285-286. 
Indicator — 

By whom invented, 168. 

Care of, 185-223-224. 

Description of, 171-175. 

How to attach, 183-185. 

Principles of, 168-171. 

Spring, 172. 

Study of diagrams, 207-230. 

Taking diagrams, 186-187- 
188. 
Isochronol governor, 202-281. 

Joule's experiments with heat, 
97-98 

Latent heat, 102-103. 
Lap — 

Effect of increasing, 134- 
145-146. 

Inside, 135-144-201. 

How to measure, 154-155. 



Lap — 

Meaning of, 201. 

Of Corliss valves, 164. 

Outside, 135-141-201. 
Lead — 

Adjustments for, 156. 

Definition of, 201. 

Equalized, 156-164.- 

Necessity of, 134. 

Of Corliss valves, 164. 
Logarithms, 197. 
Lubrication — 

Of crank pin, 279. 

Of guides, 278. 

Of pillow blocks, 280. 

Of piston, 277. 

Of valves, 277. 

Margin of safety, 13. 
Material for boilers, 14. 
Manholes, reenforcing, 24. 
Maximum theoretical duty of 

steam, 195. 
Measuring lap, 154. 
Measuring chimney draft, 124- 

125. 
Mean Effective Pressure — 

Definition of, 190. 

Figuring by ordinates, 255- 
259. 

Finding by planimeter, 262- 
263. 

Rule for finding, 220-227. 
Mechanical equivalent of heat, 

98-99. 
Momentum, 195. 
Moisture — 

In steam, 123-124. 

In coal, 124. 
Mud-drums, 43. 

Obliquity of connecting rod, 

147. 
Operation of boilers, 65. 
Ordinates, 200-255-257. 
Outside lap, 146. 

Packing for feed pumps, 80. 
Pantograph, 182-183. 
Pendulum motion, 177-182. 



INDEX 



Piston — 

Clearance, 193. 

Displacement, 193. 

Speed,. 193. 

Valve, 157. 
Placing engine on dead center, 

151-152. 
Planimeter, 262-263. 
Power — 

Calculations, 254-259. 

Definition of 194. 
Priming, 76. 

Questions — 

On boiler operation, 87-90. 
On boiler construction, 24- 

25-26. 
On boiler settings, 64-65. 
On combustion, 115-116. 
On definition of words, terms, 

and phrases, 204. 
On diagram analysis, 230- 

231-263-265. 
On engine operation, 288-290. 
On evaporation tests, 131- 

132. 
On indicator, 188-189. 
On valve setting, 166-167. 

Radius of eccentricity, 140-141. 
Ratio of expansion, 191. 
Reevaporation, 251-252. 
Reducing mechanism, 176-183. 
Relative positions of crank pin 

and eccentric, 139. 
Release, 142. 

Rocker arm, how to adjust, 150. 
Rules— 

For ascertaining required size 

of feed pump, 50-51. 
For calculations in hydraulics, 

83-86. 
For finding piston speed of 

pumps, 83-84. 
For finding strength of solid 

plate, 15. 
For finding strength of rivets, 

16 
For finding strength of riveted 
seam.s, 15. 



Rules — 

For finding area of segment 

of circle, 22. 
For finding velocity of flow 

of water in pipes, 84-85. 
For finding weight of water 

discharged per second, 85- 

86. 
For finding initial pressure „ 

220. 
For finding mean forward 

pressure, 220. 
For finding mean effective 

pressure, 220-227-228. 
For finding terminal pressure, 

242. 
For finding indicated horse 

power, 228. 
For safetv valve calculations, 

78-79./ 
For spacing braces, 23. 

Safe working pressure, 15. 
Safety Valve— _ 

How to keep in good working 
order, 80. 

Problems, computation of, 
78-79. 

U. S. marine rule for, 77. 
Sensible heat, 99-101. 
Shaking gratis, 67-68. 
Smoke prevention, 94-95. 
Specific heat, 99. 
Steam line, 209. 

Strength of riveted seams, 15, 
Strength of solid plate, 15. 
Strength of rivets, 15. 
Steam — 

Consumption per H. P. per 
hour, 198-236-238-242. 

Clearance, 193. 

Density of, 109. 

Dry, 108. 

Gaseous nature of, 107. 

In its relation to the engine, 
109. 

Efficiency of, 195-196. 

Generation of, 106. 

Method of testing dryness of 
109-124. 

Nature of, 107. 



INDEX 



Steam — 

Percentage of moisture in, 
123-124. . 

Physical properties of, 110- 
114. 

Relative volume of, 109-110. 

Saturated, 107. 

Superheated, 107-108. 

Temperature of, 107^ 

Total heat of, 108. 

Volume of, 109. 

Wet, 108. 
Surface blow off, 46-47. 
Tables- 
Analysis of coal, 92. 
Areas and circumferences of 
circles, 204-205. 

Constants for areas of seg- 
ments, 22. 

Factors of evaporation, 129. 

Constants for steam consump- 
tion per I. H. P. per 
hour, 228. 

Hyperbolic logarithms, 199. 

Lap and lead of Corliss 
valves, 164. 

Physical properties of steam, 
110-114. 

Specific heat, 99. 

Weight of water, 105. 
Temperature — 

Of escaping gases, 93. 

Of feed water, 74-123. 

Of furnace, 93. 
Tensile strength, 14. 
Terminal pressure, 190-242. 
Tests- 
Evaporation, object of, 117. 

Preparing for, 119-121. 

Duration of, 123. 

Closing of, 124. 

Record of, 127. 

Provisions for, 58-60. 

Tanks for, 59-60. 

For efficiency of boiler and 
furnace, 126. 

For efficiency of boiler, 126. 
Thermo dynamics, first law of, 

96-97-194. 
Theoretical clearance, 243-246. 
Three- wav cock, 175. 



Throttling governor, 202-276. 
Tie rods — 

For boiler walls, 31-32. 

Transverse, where to locate, 
32. 
Total heat of evaporation, 102- 

103. 
Travel of valve, 137. 
Triple riveted butt joints, 18, 

Unit of work, 194. 

Vacuum, 192. 
Valve — 

Adjustment of travel, 156. 

Corliss, how to adjust, 162. 

Diagrams, 145-148. 

Decreasing travel of, 145. 

Gear of Corliss engine, 159- 
160. 

Lap and lead of, 134-156. 

Placing central, 154-155. 

Rotative, 158. 

Slide, 133-157. 

Setting of, 133-160. 

Stem, length of, 154-155. 

Travel of, 134-137-140-155- 
201. 

Types of, 134. 
Valve, Safety — 

Frequent testing of, 79. 

Lever, 39-40-77. 

Pop, 39. 

Ratio of area to grate sur- 
face, 39-40. 

U. S. Marine rule for, 77. 
Valves — 

For feed pump, 80. 

Water — 

Boiling point of, 105-106. 
Chemical treatment of, 104. 
Composition of, 103. 
Contraction and expansion of, 

104-105. 
Foaming, 76. 
Impurities in, 104. 
Quantity required for con- 
denser, 273-276. 
Weight of, 105. 



INDEX 



Washing out Boiler. — 
Preparing for, 72. 
Proper method of, 73-74. 

Water Columns — 

Proper location of, 34-35. 
How to connect to boiler, 

35-36. 
Dangerous condition of, 37. 

Wire drawing, 191. 



Work- 
Definition of, 195. 
External, 108. 
Internal, 108. 

Wrist Plate- 
Vibration of, 162. 
Adjustment of, 163. 

Zeuner valve diagrams, 139- 
145-148. 



PART II 



STEAM ENGINEERING 



LIST OF ILLUSTRATIONS 



American underfeed stoker, 
348. 

Branca^s steam turbine, 358. 
Burke furnace, 353. 

Cahall boiler fitted with auto- 
matic stoker, 337. 

Curtis steam turbine (general 
view), 372. 

Curtis steam turbine, under 
construction, 373. 

Curtis steam turbine — station- 
ary and revolving buckets, 
374. 

Curtis steam turbine — nozzle 
diaphragm, 375. 

De Laval steam motor — gen- 
eral view, 394. 

De Laval diverging nozzle, 392. 

De Laval turbine wheel and 
nozzles, 393. 

De Laval steam turbine — work- 
ing parts, 396. 

De Laval steam turbine — plan 
view, 398. 

De Laval steam turbine — sec- 
tional view, 399. 

De Laval steam turbine — gov- 
ernor and valve, 402. 

De Laval steam turbine — cross 
section of wheel, 404. 

Diagram of nozzles and buckets 
in a Curtis steam turbine, 
376. 

Double riveted lap joint, 305. 

Double riveted butt joint, 306. 

Double crow foot stay, 318. 



Electrically operated valve 
(Curtis turbine), 380. 

Governor of Curtis steam tur- 
bine, 379. 

Hamilton-Hplzwarth steam 

turbine, 385. 
Heroes steam turbine, 357. 

Jones underfeed stoker, 351. 

Mansfield chain grate stoker, 

338. 
Murphy furnace, 344. 

Playford stoker, 339. 

Quadruple riveted butt joint, 
309. 

Roney stoker, 346. 

Triple riveted butt joint, 307. 

Vanderbilt locomotive fire box, 

. 14. 
Vica.s mechanical stoker, 341. 

Wilkinson mechanical stoker, 

342. 
Westinghouse- Parsons steam 

turbine (general view), 360. 
Westinghouse - Parsons steam 

turbine (sectional view), 362. 
Westinghouse - Parsons steam 

turbine — open for inspection, 

361. 
Westinghouse - Parsons steam 

turbine governor, 367. 



PART II 



STEAM ENGINEERING 



INDEX 



Accumulator, 372. 

Action of steam in turbine en- 
gines, 364-377-398. 

Adiabatic expansion, 392. 

Admission of steam to turbine 
engines, 370-379. 

American stoker, 347-348-349. 

Angle irons, 314. 

Area — 

Of segments, 320-321. 

Of surface to be stayed, 319. 

Balancing pistons, 365. 
Barometric condenser, 408. 
Boiler — 
cCare of, 327. 
Braces and stays, 311. 
Belpaire type, 313. 
Fire cracks, 331. 
How to prepare for washing 

out, 328. 
How to fire up, 331-332. 
How to connect with main 

header, 332. 
Inspection of, 330. 
Rivet material, 298. 
Stay bolts, 313. 
Steel plate — specifications 

for, 296. 
Tensile strength of plate, 

296. 
Thurston^s specifications for 

rivets, 298. 

Calculating strength of stayed 

surfaces, 319. 
Channel bar, 317. 
Clearance in turbine engines, 

365-374-383. 
Clinker on furnace walls, 330. 
Coxe mechanical stoker, 338. 



Crown — 

Bars, 313. 

Bolts, 313. 

Sheet, 313. 
Crow foot brace, 311-312. 
Curtis steam turbine, 370. 

Action of steam in, 377. 

Efficiency of, 381. 

Expanding nozzles of, 371. 

Guide bearings of, 373. 

Lubrication of, 371. 

Ratio of expansion in four 
stage machine, 371. 

Stationary blades — function 
of, 374. 

De Laval steam turbine, 392. 

Action of steam in, 397-400. 

Conversion of heat into work, 
395. 

Diverging nozzles of, 392. 

Efficiency, tests of, 404-405. 

Flexible ' shaft of, 400-402. 

Gear wheels of, 400. 

Governor, 402-403. 

Vacuum valve, 403. 
Diameters of rivets, 299-300. 
Dished heads, 325. 
Double riveted butt joints, 299- 

303-306. 
Double riveted lap joints, 300- 

305-306. 
Double crow foot brace, 318. 

Efficiency — 

Of double riveted lap joint, 

305-306. 
Of double riveted butt joint, 

307. 
Of triple riveted butt joint. 

307. 



INDEX 



Efficiency — 

Of quadruple riveted butt 

joint, 309-310 
Of Westinghouse - Parsons 

steam turbine, 368. 
Of Curtis steam turbine, 380- 

381. 
Of De Laval steam turbine, 

404. 

Factor of safetv, 324. 
Flexible coupling, 366-387. 
Flexible shaft, 400. 
Floating journal, 366. 
Floating fulcrum, 367. 
Fusible plug, 329. 

Gusset stays, 314. 

Hamilton - Holzwarth steam 

turbine, 382. 
Action of steam in, 385-386. 
Development of, 382. 
Distribution of steam in, 

386. 
Device for changing speed of, 

389. 
Flexible couplings of, 387. 
Governor, 387-388. 
Lubrication of, 390. 
Regulating mechanism, 388- 

389. 
Running wheels, 384. 
Stationary disks, 383. 
Thrust ball bearing, 387. 

Inspectors, U. S. Board of, 

296-311. 
Inspection of boilers, 330. 

Jones underfeed stoker, 351- 
352. 

Kinetic energy of steam, 357- 
391-400. 

Lost work, 368. 

Man-holes for boilers, 330. 
Mechanical stokers, 334. 
Murphy furnace, 341-342-343. 



Nozzle — 

Expanding, 391-395. 
Valves, 395. 

Outside furnaces, 353-354. 

Parallel flow of steam in tur- 
bine engines, 359. 

Pitch— 

Of rivets, 299-300. 
For stays, 319. 

Playford stoker, 339. 

Punched and drilled boiler 
plates, 297. 

Quadruple riveted butt joint, 

308. 
Quintuple riveted butt joint, 

308. 

Rivets — 

Crushing resistance of, 305. 

Diameter and pitch of, 300. 

Material for, 297. 

Shearing strength of, 298. 
Riveted joints — 

Calculations for efficiencies 
of, 306-307-308-309-310. 

Double lap and butt, 302. 

Single lap, 302. 

Triple riveted butt, 303. 

Quadruple riveted butt, 309. 

Quintuple riveted butt, 309. 
Riveting machine, 302. 
Roney stoker, 345-346 

Stayed surfaces — 

Areas of, 320. 

Strength of, 319-320-323. 
Steam turbine — 

Branca's turbine, 359. 

Disposal of exhaust steam, 
406. 

Efficiency of, 381. 

Hero's turbine, 359. 

Main requisite for quiet lun- 
ning, 387. 

Two main sources of econ- 
omy, 380-411. 

Types of, 359. 



INDEX 



Tables — 

Diameters of rivets, 298. 

Diameters and pitch of rivets 
in double riveted joint, 
300. 

Kent's rules for thickness of 
plate and diameter and 
pitch of rivets, 301. 

Lloyd's rules for thickness of 
plate and diameter of riv- 
ets, 300. 

Proportions of single riveted 
lap joints, 302. 

Proportions of double riveted 
lap and butt joints, 303. 

Proportions of triple riveted 
butt joints, 304. 

Through stays, 314-316-317. 

Thurston's table of joint ef- 
ficiencies, 301. 

Triple riveted butt joint, 303- 
304-307. 
Turbines (steam) — 

Branca's turbine, 359. 

Disposal of exhaust steam, 
406. 

Efficiency of, 380. 

Hero's turbine, 359. 

Main requisites for quiet run- 
ning, 387. 

Types of, 359. 

Unstayed surfaces — 

Rule for finding strength of, 
324. 



Vacuum- 
Advantages of, 407-409. 
Valve, 403. 

Vanofcxl'^^ locomotive fire box, 
313. 

Velocity — 
Force of, 380. 

Of escaping steam, 360-361. 
Work done by, 377-378. 

Vicars mechanical stoker, 340. 



Water column for boiler, 330. 
Welded seams, 325. 
Westinghouse - Parsons steam 

turbine — 

Action of steam in, 364-365. 

Clearances in, 364. 

Efficiency of, 369. 

Floating journal, 367. 

Governor, 367. 

Principles of, 359. 

Perfect balance of, 368. 

Speed of, 360. 

Stationary and moving 
blades of, 363-364. 
Wheels — 

Impulse, 360. 

Reaction, 360. 

Running, 384. 
Wilkinson stoker, 340^341 



INDEX— ADDENDA 



Absorption system of refrigera 
tion 451-456. 
Method of operation, 451. 
By whom invented, 452. 
Advantages of, 452. 
Apparatus required, 452-456. 
Action of pump valves, 510-512- 

516-518. 
Air compressors, 488. 
Air compressor governor, 493 
Allis Chalmers steam tur- 
bine, 411-412. 
Action of steam in, 411. 
Balance pistons, 411. 
Clearance between blades, 

413. 
Trust bearing, 413-414. 
Method of fitting blades in, 

414-415. 
Foundation rings, 416. 
Shroud rings, 418. 
Bearings — Construction of, 

418. 
Lubrication, 418. 
Floating journals, 421. 
Speed regulation, 422. 
Bed plate, 423. 
Anhydrous ammonia, 428-451. 
Composition of, 428-429. 
Compression of, 428. 
Atmospheric pressure, 510-514- 

515. 
Automatic receiver and pump, 

537. 
Automatic cut off, 558. 

Blading of steam turbine, 414- 

415-416. 
BrJne system of refrigeration, 

438-439. 
Buffalo Duplex steam pump, 

524-525-526-528. 

Cameron steam pump, 519-520- 

521-522. 
Carre's refrigerating apparatus, 

452-455. 
Compound and multiple stage 

air compression, 488. 



Compression^ system of re- 
frigeration, 429. 

Corliss engine valve gear, 478. 

Cylinder lubrication, 558-559- 
560. 

Dean steam pump, 523-524-525- 

536. 
De La Vergne ice machine, 444. 
Characteristic features of, 

444. 
Method of sealing stuffing 

box, 444-445. 
Valves, 445. 
Diagram from, 449. 
Detroit lubricator, 559-560-563. 
Diagrams from Linde ice ma- 
chine, 432-433. 
Dietz force feed lubricator, 569- 

571. 
Dynamometer, 551. 

Economical use of oil, 421. 
Electric compressors, 490. 
Elementary Parsons type of 

steam turbine, 414. 
Emerson steam pump, 528-530- 

532-538. 
Engine bearings, 548. 

Lubrication of, 549-550. 
Epping-Carpenter steam pump, 

525-527-529-532. 

Featherstone ice machine, 456. 
Flexible coupling, 422. 
Floating journals, 421. 
Foundation rings, 416. 
Freezing mixtures, 424. - 
Friction, 544. 

Law of, 544-546. 

Uses of, 545-546. 

Kinds of, 546. 

Coefficient oi, 546-547-548. 

Loss per H. P., 552-553. 

Of piston rod, 550-551. 

Gaseous ammonia, 428. 
Liquefication of, 428. 
Condensation of, 428-431. 
Compression of, 428. 



INDEX — ADDENDA 



Graphite, 555. 

Essential function of, 556. 

Advantages in use of, 556- 
557. 

How to use in engine cylin- 
der, 565-566-567. 

Tests of, 556-557. 

Heat, nature of, 424-425-426. 
Abstraction of, from various 

bodies, 424-427. 
Waste of, 423. 
Height— 

That water will rise by suc- 
tion, 516-518. 
High speed, horizontal, piston 
valve engine, 483. 

Ice making, 424-441. 

Systems of, 441-443. 
Interior lubrication, 558. 
Internal friction, 554. 

Journals of steam turbine, 421. 



Linde ice machine, 429-431. 
Diagrams from, 432-433. 
Clearance of piston and 

cylinder head, 434. 
Construction of cylinder 434' 

435. 
Lubrication of, 435. 
Valves of, 436. 
Stuffing box, 436-438. 
Lubricant, nature of, 553. 

Quality of, 553. 
Lubrication of steam turbine, 

418. 
Lubrication, 546. 
Cost of, 557. 
Importance of, 546-556. 
Of piston rods, 553-554. 
Of valves and pistons, 560. 
Lubricated surfaces, 555. 
Lubricating appliances, 561. 
Lubricating oils, 555-556-557 
560. 

Manzel oil pump, 567-568. 
Method of application, 570. 



Mechanical refrigeration, 424- 

426. 
Theory and practice of, 424- 

427. 
Monitor sight feed-lubricator, 

572. 

Nitrogen in ammonia, 428. 

Oils, how to test, 554-558. 
Oiling the piston rod, 552. 

Packing, 550. 

For piston rod, 550-551. 

For valve stem, 550. 
Piston rod, 551. 

Friction of, 551. 

Lubrication of, 551-552. 
Powell Lubricator, 564-565-566. 
Pumps, 510. 

Most simple form of, 513-514. 

Theory and principles of ac* 
tion, 514-515-516. 

Double acting, 516. 

Single acting, 517. 

Force required to operate, 
516-517. 

Duplex, 524-534-544. 

Steam, 519. 

Power, 519-527-534-536. 



Questions on compound and 
multiple stage air compres- 
sion, 508. 

Questions on pumps, 540-544. 

Recce's apparatus for refrigera- 
tion, 455-456. 
Refrigeration, 424-427. 

Agents employed in, 428-45L 

Mechanical, 424. 

Methods of utilizing, 438-440 

Systems of, 427. 
Refrigerating machine, 426. 
Rochester force feed lubricator, 

572. 
Rotor of steam turbine, 417. 

Safety governor, 422. 
Setting and operating air com- 
pressors, 494. 



INDEX — ADDENDA 



Single Cylinder direct acting, 
524. 
Sinking, 527. 
Triplex power, 535. 
2\utomatic, 537. 
Sight feed lubricator, 559. 
Smith-Vaile power pump, 527- 

535. 
Steam, elasticity of, 527. 
Steam strainer, 422. 
Steam turbine — Allis Chalmers, 

411-421. 
Systems of Refrigeration, 427- 
429-439. 
By absorption, 427-451. 
By compression, 429. 
Wet, 429-431. 
Dry, 432. 
Systems of utilizing refrigera- 
tion, 439-443. 
Brine, 438-439, 
Direct expansion, 439-440. 



Tables, 499-507. 
Testing of oils, 554-559. 
Triumph ice machine, 449-450. 

Auxiliary suction valve, 450. 

Method of packing piston 
rod, 451. 

Vacuum — 

How created, 514-515. 
Valves — 

Balance throttle for steam 
turbine, 422. 

Suction and discharge for 
Triumph ice machine, 450. 

Automatic, 510-511. 

Double beat, 510. 

Hinged, 510-511. 

Lift of, 517-518-519. 

Material for, 512. 

Worthington steam pump, 525. 



INDEX 



ELECTRICITY FOR ENGINEERS 



Ammeters, 137. 

alternating current, 143. 

shunt, 138.^ ^ 
Ampere, definition of, 7. 

hour, definition of, 9. 

milli, definition of, 10. 

turns, definition of, 42. 
Arc Lamp, alternating current, 
168. 

brush, 155. 

constant current, 154. 

constant potential, 165. 

enclosed, 167. 

principle of, 153. 

Thomson-Houston, 160. 

Western Electric, 169. 
Armature, location of faults, 61. 

Balanced three- wire system, 

23. 
Booster, 198. 
Brush system, 77. 

controller, 84. 
Brushes, care of, 53. 

construction of, 53. 

shifting of, 62. 

setting of, 59. 

staggered, 55. 

Calculation of wires, 25. 
Center of Distribution, 25. 
Circuit breakers, 117. 
Circular mil, definition of, 26. 
Collector rings, 125. 
Coulomb, definition of, 10. 
Commutator, area allowed for 
current, 51. 

care of, 53. 

construction of, 49. 
Conductivity, definition of, 16. 
Conductors, 7. 
Constant current system, 20. 



Constant potential system, 20. 
Current, 5. 

generation of, 40. 

single phase, 129. 

two and three phase, 130. 
Cut-out box, ?5. 

Distributing center, 24. 
Divided circuits, 16. 
Dvnamos, alternating current, 
122. 

brush, 77. 

care of, 64. 

compound wound, 47. 

failure to generate, 67. 

operation of constant cur- 
rent, 75. 

operation of constant poten 
tial, 65. 

operation in parallel, 69. 

reversal of current, 44. 

separate exciting, 123. 

series, connections of, 45 

shunt, connections of, 46. 

test for polarity, 70. 

Thomson-Houston, 89. 

Electromagnet, 41. 
Electromotive force, definition 

of counter, 108. 
Electroplating, 199. 
Electrolysis, 199. 
Electrolytic action, 9. 
Equalizer bar, 72. 

Feeders, 24. 
Fuses, 117. 

Gramme Ring, 44. 
Ground detectors, 185. 

Heating by electricity, 201^ 
Horse power, 15. 



INDEX 



Incandescent lamps, 172. 

current required, 175. 

efficiency tables, 173. 
Insulators, 7. 

Joints in wires, 31. 
Joule, 15. 

Kilowatt hour, 15. 

Laminated armature, 53. 
Light, absorb tion of, 176. 
Lightning arrest^ts, 204. 

Thomson, 206. 
Lines of force, definition of, 41. 

direction of, 42. 
Loss in wires, 27. 

Magnet, soft iron, 5. 

steel, 5. 
Meters, reading of, 147. 
Mil, circular, 26. 

square, 26. 
Motors, 107. 

alternating current, 116, 

compound, 112. 

series, 111. 

shunt, 110. 
Multiple arc system, 20. 
Multiple series system, 21, 

Negative wire, 23. 
Nernst lamp, 177. 
Neutral point of dynamo, 49. 
Neutral wire, 22. 

Ohm, 13. 
Ohm's law, 14. 

Parallel system, 19. 
Photometer, Bunsen, 190. 

Rumford's, 191. 
Polarity indicator, 142. 
Positive wire, 23. 
Potential, difference of, 10. 
Prony brake, 187. 

Regulator, Brush, 85. 
series dynamo, 45. 



Resistance box, 46. 

definition of, 13. 

effect of heat on, 13. 
Rheostat for shunt dynamo, 66. 

Series arc system, 20. 

circuit, 6. 

multiple system, 20. 
Service wires, 25. 
Short circuit, 11. 
Speed controller, 114. 
Square mil, 26. 
Static electricity, 12. 
Storage batteries, 193. 

connections for, 197. 
Switchboard, arc, 101. 

arc, 104. 

constant potential, 73. 

Testing lines, 181. 

dynamo efficiency, 187. 

grounds, 184. 

open circuits, 181. 

short circuits, 183. 
Thomson-Houston system, 89 

controller, 97. 
Three-wire system, 22. 
Transformer, principle of, 130 

rotary, 128. 

Volt, definition of, 10. 
Voltameter, 9. 
Voltmeter, 10. 

alternating current, 143. 

magnetic vane, 137. 

Weston, 133. 

Watt, definition of, 14. 

hour, definition of, 15. 
Wattmeters, 144. 

Thomson, 145. 
Wires, carrying capacity of, 38 

properties of, 39. 

weights of copper, 37. 
Wiring tables, 32. 
Wiring systems, 19. 



INTRODUCTION 



ENGINEERING DIVISION 



In the following pages the author proposes to deal 
mainly with the operation of steam engines, boilers, 
feed pumps, and all the necessary adjuncts of a steam 
plant, rather than with the construction and erection of 
the same, although the designing and construction of 
steam machinery will receive some attention. 

In order to successfully operate a steam plant the 
engineer in charge should, in addition to his other 
accomplishm^ents, have at least sufficient technical 
knowledge to enable him to ascertain, by measure- 
ments and calculations, such very important points as 
the safe working pressure of his boiler, the most eco- 
nomical point of cut off for his engine, whether engine 
and boiler are properly proportioned for the work to 
be performed, and many other details which will be 
treated upon in their proper place. 

Without a doubt the most successful operating 
engineers are those who combine practice with theory, 
and in order to obtain a practical working knowledge 
of steam engineering it is absolutely necessary that 
the young man who desires to become a successful 
engineer should start in the boiler-room, that he 
should thoroughly familiarize himself with all of the 
details of boiler management, and while his hands 
and eyes are thus gradually being trained to the prac- 
tical part of the work he should at the same time be 
training his. mind in the theoretical part by reading 
and studying technical books and journals reJati^^e to 
steam engineering. In order to facilitate this won . 

9 



10 INTRODUCTION 

series of practical questions will follow the close of 
each chapter, the answers to which may be found in 
the matter contained in the chapter. And now with 
the hope that a study of the following pages may prove 
to be a help to all into whose hands this book may 
come, the author respectfully dedicates it to his fellow 
craitsmen, the engineers of America. 

C. F. S. 



Engineering 

CHAPTER I 
THE BOILER 

Description of various types — Construction — Rules for ascertain- 
ing strength of sheet before and after punching — Strength of 
rivets — Single and double riveted seams — Triple riveted butt 
joints, strength of — Force tending to rupture a boiler — Rules 
for finding the safe working pressure of boilers — Bracing — 
Rules for bracing — Bracing domes. 

It is hardly within the scope of this book to describe 
the many and varied types of metallic vessels known 
as steam boilers in use to-day for the generation of 
steam for power and other purposes. The author will 
deal mainly with those types most commonly used in 
this country for stationary service. 

Description. These may be divided into four differ- 
ent classes. The first and most simple type, and the 
one from which the others have gradually evolved, is 
the plain cylinder boiler in which the heated gases 
merely pass under the boiler, coming in contact only 
with the lower half of the shell and then pass to the 
stack. These boilers are generally of small diameter 
(about 30 in.) and great length (30 ft.). Next comes 
the flue cylindrical boiler, which is somewhat larger in 
diameter than the former, generally 40 in. diameter 
and 20 to 30 ft. long, with two large flues 12 to 14 in. 
diameter extending through it. The return tubular 
boJler, consisting of a shell with tubes of small diam- 

11 



12 



ENGINEERING 



eter (2 to 4 in.) extending from head to head through 
which the hot gases from the furnace pass on their 
way to the stack. This boiler, which comes in the 
third class, is probably more extensively used in the 
United States for stationary service than any other 
type. The fourth class comprises the water tube boil- 
ers, in which the water is carried in tubes 3 to 4 in. in 
r^'ameter, sometimes vertical and sometimes inclined, 
and connected at the top to one end of a steam drum, 




STANDARD HORIZONTAL BOILER WITH FULL-ARCH FRONT SETTING. 



and having the lower ends of the tubes connected to a 
mud drum, which is also connected to the opposite end 
of the steam drum, thus providing for a free circula- 
tion of the water. Of the latter type there have been 
many different kinds evolved during the last one hun- 
dred years, the majority of them having had but a 
brief existence, being compelled to obey the inex- 
orable law of the survival of the fittest, and to-day 
there are a few excellent types of water tube boilers 



THE BOILER 



13 



which have become standard and are being extensively 
used. The margin of safety as regards disastrous 




WICKES VERTICAL WATER TUBE BOILER. 

explosions appears to be in favor of the water tube 
boiler. It is not contended that they are entirely 



14 



ENGINEERING 



exempt from the danger of explosion. On the con- 
trary, the percentage of explosions of water tube boil- 
ers in proportion to the number in use is probably as 
large, if not larger, than it is with boilers of the shell 
or return tubular type, but the results are seldom so 
destructive of life or property, for the reason that if 
one or more of the tubes give way the pressure is 
released and the danger is past. 




500 HORSE POWER HEINE WATER TUBE BOILER. 



Construction. As the four classes of boilers above 
referred to are constructed of similar material, although 
assembled in different ways, the standard rules for 
calculating strength of joints, bracing, etc., may be 
applied to all. 

The shell should be made of homogeneous steel of 
about 60,000 lbs. tensile strength. The thickness 
depending upon the pressure to be carried. The term 



THE BOILER 15 

tensile strength means that it would take a pull of 
60,000 lbs. in the direction of its length to break a bar 
of the material one inch .square, or two inches wide by 
one-half inch thick, or three-eighths of an inch thick 
by 2.67 in. wide. 

The heads are generally made one-eighth of an inch 
thicker than the shell. 

Riveting. Boiler rivets should be of good charcoal 
iron, or a soft, mild steel of 38,000 lbs. to 40,000 lbs. 
T. S. No boiler is stronger than its weakest part, and 
it is evident that a riveted joint has not the full 
strength of the solid plate. In order to ascertain the 
safe working pressure of a boiler it is necessary to first 
determine the strength of the riveted seams, and the 
method of doing this is as follows: Assume the boiler 
to be of the horizontal tubular type, 60 in in diameter 
by 16 ft. in length. The plates to be of steel ^ in. 
thick, having a tensile strength of 60,000 lbs. per 
square inch, the longitudinal seams to be double 
riveted and the girth seams to be single riveted. The 
pitch of the rivets, that is the distance from the center 
of one rivet hole to the center of the next one in the 
same row, to be for the double riveted seams 3^^ in. 
and for the single riveted seams 2^ in. The diameter 
of the rivets to be ^ in. and diameter of holes to be 
\\ in. Assume the rivets to have a T. S. of 38,000 lbs. 
per square inch of sectional area. First, find strength 
of a section of solid plate 3^ in. wide, which is the 
width between centers of rivet holes before punch- 
ing. 

Rule /. Pitch x thickness x T. S. Thus, 3.25 x .375 x 
60,000= 73,125 lbs., strength of solid plate. 

Second, find strength of net section of plate, mean- 
ing that portion of plate left after deducting the diam- 



m 



ENGINEERING 



eter of one hole || in., which expressed in decimals 
= .9375 in. from the width of plate before punching. 

Ru/e 2. Pitch — diameter of hole x thickness x T. S. 
Thus, 3.25 - .9375 X .375 X 60,000 = 52,031 lbs., strength 
of net section of plate. 

Third, find strength of rivets. In calculating the 
strength of rivets in a double riveted seam, the sec- 
tional area of two rivets must be considered, taking 




BABCOCK AND WILCOX BOILER. 



one-half the area of two rivets in the first row, and the 
area of another rivet in the second row. The area of 
a ^-in. rivet is .6013 in., but when in position it is 
assumed to fill the hole \\ in. Consequently, its area 
would then be .69 in. and its strength is found by 
Rule 3. 

Rule 3, Sectional area x T. S. Thus, .69x38,000 = 
26,220 lbs., strength of one rivet, and multiplying by 2, 
as there are two rivets, the result is 26,220 x 2 = 52,440 



THE BOILER 



17 



^bs., strength of rivets in the seam under considera- 
lion. It thus appears that the plate is the weakest per- 




VERTICAL FIRE BOX BOILER. 



tion and the percentage of strength retained is found 
by multiplying 52,031 by lOO and dividing by 73,125, 



IS ENGINEERING 

XL t 1-j 1 X -T^u 52,031x100 

tnc Strength of solid plate. Thus, =71.1 

^ ^ 73,125 ^ 

per cent. 

The query might arise, why is the diameter of one 
rivet hole deducted from the pitch when figuring the 
strength of net plate? The answer is, that in punching 
the holes one-half the diameter of each hole is cut 
from the section designated, thereby reducing its width 
by just that amount. 

The 71. 1 per cent, obtained by the calculation rep- 
resents the strength of the boiler as compared to the 
strength of the sheet before punching, and should enter 
into all calculations for the safe working pressure. 

It is usual in practice to figure the strength of a 
double-riveted seam at 70 per cent, of the strength of 
the solid plate. The strength of triple-riveted butt 
joints may be calculated by taking a section of plate 
along the first row of rivets and estimate it as a single- 
riveted joint, then add to this result the strength of 
rivets in the second and third rows for a section of the 
same width. In properly designed triple-riveted butt 
joints the percentage of strength retained is 88, and 
some recent achievements in designing have shown the 
remarkable result of quadruple-riveted butt joints 
retaining as high as 92 to 94 per cent, of the strength 
of the solid plate. 

Bursting Pressure, The query might arise, why 
should the longitudinal or side seams require to be 
stronger than the girth or round about seams? The 
answer is, that the force tending to rupture the boiler 
along the line of the longitudinal seams is proportional 
to the diameter divided by two, while the stress tend- 
ing to pull it apart endwise is only one-half that, or 
"proportional to the diameter divided by four- 



THE BOILER 19 

To illustrate, let Fig. i represent the shell of the 
boiler heretofore referred to, ignoring for the time 
being the tubes and braces, and consider the boiler 
simply as a hollow cylinder. Now the total force 
tending to rupture the boiler along the line of the girth 
seams or in the direction of the horizontal arrows = area 
of one head in square inches x pressure in pounds per 
square inch. It is true that the pressure is exerted 
against both heads, but the area of one head can only 
be considered for the reason that the two stresses are 
exerted against each other just as in the case of two 
horses pulling against each other, or in opposite direc- 
tion on the same chain. T^e *=tress on the chain will 




I 



AJL 







FIGURE 1. 

be what each horse (not both) pulls. To further illus- 
trate, suppose one of the horses to be replaced by a 
permanent post or wall and let one end of the chain be 
attached thereto. One head or one side of the boiler 
pulls against the other, and the stress on the seams is 
the force with which each (not both) pulls. Referring 
again to Fig. i, area of one head = 60^ x .7854 = 2827.4 
sq. in. Suppose there is a pressure of 10 lbs. per 
square inch in the boiler. Then total stress on the 
girth seams = 2827.4 x 10 = 28,274 lbs. Opposed to this 
pull is the entire circumference of the boiler, which is 
60 X 3.1416 = 188.5 ^^- Therefore, dividing total pres- 
sure (28,274 lbs.) by the circumference in inches (188. 5) 
will give 150 lbs. as the stress on each inch of ihe 



20 ENGINEERING 

girth seams. While the stress on each inch of the 
longitudinal seams or along the line A B, Fig. i, and 
which is exerted in the direction of the vertical arrows, 
is pressure (lO lbs.) x one-half the diameter (30 in.) 
= 300 lbs. One-half the diameter is used because the 
pressure in any direction is effective only on the sur- 
face at right angles to that direction. 

The formula for finding the bursting pressure of a 
boiler may be expressed as follows: 

T S X T . 

B = -p in which B = bursting pressure. 

T.S. = tensile strength. 
T= thickness of sheet. 
R= radius or one-half the diam. 
Example. T. S. = 55,000 lbs. per square inch. 

T = ^ in. (expressed decimally = .375 

in.). 
R = 30 in. 
Then 55,000 x .375 ^ 30 = 687.5 ^^s. per square inch, 
which is the pressure at which rupture would take 
place provided there were no seams in the boiler and 
the original strength of the sheet was retained, but, as 
has been seen, a certain percentage of strength is lost 
through punching or drilling the necessary rivet holes, 
and this must be taken into account. 

The formula now becomes, for double riveting, 

B = ' ' — , in which the letters preserve the same 

value as in the original formula, but the result is 
reduced by multiplying by the decimal .70, which rep- 
resents the percentage of strength retained by double- 
riveted seams. Consequently B will now = 

55,ooox.375x.7o gilbs. 
30 

Ir case the seams are all single riveted .56 must be 



THE BOILER 21 

substituted for .70, and with triple-riveted butt joints 
.88 can safely be used. 

Safe Working Pressure. In order to ascertain the safe 
working pressure of a boiler it is necessary first to cal- 
culate the bursting pressure and divide this by another 
factor called the factor of safety. The one most com- 
monly used for boilers is 5, or in other words the safe 
working pressure = one-fifth the bursting pressure. In 
the case of the boiler under consideration, the safe 
pressure would be 481 -^ 5 = 96 lbs,, at which point the 
safety valve should blow off. 

Bracing, Every engineer can easily ascertain for 
himself whether the boilers under his charge are 
properly braced or not. The parts that require bra- 
cing are: all flat surfaces, such as the sides and top of 
the fire-box in boilers of the locomotive type, and 
those portions of the heads above and below the tubes 
in horizontal tubular boilers, also the top of the dome. 

The stress per square inch of sectional area on braces 
and stays should not exceed 6,000 lbs. It is custom- 
ary to consider the flange of the head and the top row 
of tubes as sufficient bracing for a space two inches 
wMde above the tubes and the same distance around the 
flange. Therefore the part of the head to be braced 
will be the segment contained within a line drawn two 
inches above the top row of tubes and two inches inside 
the flange. 

In order to ascertam the number of braces required 
for a given boiler head, three factors are necessary: 
first, the area of the segment in square inches; second, 
the diameter and T. S. of the braces, and third, the 
pressure to be carried. By the use of Table No. i the 
areas of segments of boiler heads ranging from 42 to 72 
in. in diameter can easily be obtained. Assume the 



22 



ENGINEERING 



boiler to be 6o in. in diameter, distance from top of 
tubes to top of shell 24 in. Deduct 4 in. for surface 
braced by top row of tubes and flange, leaving the 
height of segment to be braced 20 in. 



TABLE I 



Diameter 
of Boiler. 


Ditsance from 
Tubes to Shell. 


Height of 
Segment. 


Constant. 




42 in. 


15 in. 


II in. 


.16314 




44 m. 


17 in. 


13 in. 


.1936 




48 in. 


19 m. 


15 111- 


.20923 




54 m. 


21 in. 


17 m. 


.21201 




60 in. 


24 m. 


20 m. 


.22886 




66 in. 


25 in. 


21 m. 


.214 




72 m. 


29 in. 


25 m. 


.24212 





Rule, Multiply the square of the diameter of the 
boiler by the constant number found in right hand col- 
umn opposite column headed diameter. 

Example. 60 x 60 x .22886 = 823.89 sq. in., area of 
segment to be braced. Find number of braces 
required. Assume the braces to be \yi in. in diam- 
eter and of a T. S. of 38,000 lbs. per square inch of 
section. The area of one brace will be .994 sq. in., 
which X 6,000 lbs. gives 5,964 lbs. as the stress allow- 
able on each brace. Suppose the pressure to be car- 
ried is 100 lbs. per square inch. There will be area of 
segment (823.89 sq. in.) x pressure (100 lbs.) = 82,389 
lbs., total stress. Dividing this result by 5,964 lbs. 
(the capacity of each brace) gives 13.8 braces as the 
number needed. In practice there should be fourteen. 

Having a T. S. of 38,000 lbs. and using 6 as the 
factor of safety, each brace could safely sustain a pull 
of 6,295 lbs. Therefore it is evident that the above 
mentioned load for each brace is well within the limit. 
For convenience in calculating the areas of segments 




THE BOILER 23 

of circles, other than those mentioned in Table i, the 
following rule is given: 

Referring to Figure 2 it is desired to find the area of 
the segment contained within the lines A B C E. It 
will be necessary first to find the area of the sector 
bounded by the lines A B C D. This is done by mul- 
tiplying one-half the length of 
the arc, A B C, by the radius, 
D B. Having obtained the 
area of the sector, the next 
step is to find the area of the 
triangle bounded by the lines 
A E C D and subtract it from 
the area of the sector. The 
remainder will be the area of figure 2. 

the segment. Having found 

the area of the surface to be braced, and the number 
of braces required, it now becomes necessary to consider 
the spacing of the same. 

Rule, Divide area to be braced by the number of 
braces, and extract the square root of quotient. 

Example. 823.89^14=58.8 sq. in. to be allotted to 
each brace. Extract square root of 58.8 and the 
result is 7.68 inches, which is the length of one side of 
the square which each brace will be required to sus- 
tain. 

For internally fired boilers the same rules can be 
applied except that the surfaces to be braced are 
generally of rectangular shape and consequently the 
area is more easily figured than in the case of seg- 
ments. That part of the head below the tubes also 
requires to be braced, and ' two braces are generally 
sufficient, as at A and B, Fig. 3. In the case of domes 
it is safe to consider the portion of the head within 



24 



ENGINEERING 



three inches of the flange as sufficiently braced. Then 
suppose the dome to be 36 in. in diameter^ there will 
remain a circle 30 in. in diameter to be braced. The 
circumference of this circle is 94.2 in. and the pitch, 
or distance from center to center of the braces^ being 

7.6 in.^ the number of 
braces required is 
found by dividing 94.2 
b y 7-6, giving 12 
braces. These braces 
should be located 
along a line which is 
one-half the pitch, or 
3.8 in., within the cir- 
cumference of the 30- 
in. circle. The space 
immediately surround- 
ing the hole cut for 
the steam outlet will 
b e sufficiently reen- 
forced by the flange riveted on for the reception of the 
steam pipe. All holes cut in boilers, such as man 
holes, hand holes, and those for pipe connections, 
above two inches should be properly reenforced by 
riveting either inside or outside a wrought-iron or steel 
ring or flange of such thickness and width as to con- 
/tain at least as much material as has been cut from the 
hole. 

Questions 

1. How many types of steam boilers are there? 

2. What kind of boilers are included in type one? 

3. Describe a boiler belonging to type two. 

4. Describe a boiler of the third type. 




FIGUEE 3. 



THE BOILER 25 

5. How is a boiler of the fourth type constructed? 

6. In what respect do water tube boilers have the 
advantage over other types as regards explosions? 

7. What kind of material should be used in the con- 
struction of boilers? 

8. What does the term tensile strength (T. S.) 
mean? 

9. What is the usual T. S. of steel boiler plates? 

10. How much thicker than the shell plates should 
the heads be? 

11. Of what material and of what T. S. should the 
rivets be? 

12. Is a riveted joint as strong as the solid plate? 

13. What is meant by the pitch of the rivets? 

14. What is the usual pitch for a double riveted 
seam.? 

15. Give the rule for finding the strength of the solid 
plate before punching. 

16. What is meant by net section of plate? 

17. What is the rule for finding strength of net sec- 
tion of plate? 

18. How is the strength of rivets in a double riveted 
seam calculated? 

19. What percentage of the strength of soh'd plate is 
usually retained in a double riveted seam? 

20. How is the strength of a triple riveted butt strap 
joint calculated? 

21. What per cent, of the original strength of the 
sheet is retained in a properly designed triple riveted 
butt strap joint? 

22. Why should the side seams be stronger than the 
girth seams? 

23. What is the rule for finding the bursting pressure 
of a boiler? 



26 ENGINEERING 

24. How is the safe working pressure of a boiler 
calculated? 

25. What parts of a boiler require bracing internally? 

26. What stress per square inch of sectional area 
may be allowed on braces? 

27. How is the number of braces required for any 
part of the boiler obtained? 

28. How should domes be braced? 



CHAPTER II 
BOILER SETTINGS AND APPURTENANCES 

Foundations— Brick work, etc. — Grate surface — Insulation — Water 
columns — Steam gages— Safety valves — Rules for finding 
areas of — Fusible plugs and where to place them — Domes and 
mud drums — Feed pipes — A good arch for the back connec- 
tion — Blow off pipes and cocks — Surface blow off and circulat- 
ing system — Feed pumps and feed water heaters— Injectors — 
Saving effected by heating the feed water with exhaust 
steam — Apparatus for making coal tests— Heating surface — 
Rules for figuring the same. 

Settings. In the case of internally fired boilers the 
matter of setting resolves itself into the simple point 
of securing a sufficiently solid foundation, either of 
stone or brick laid in cement, for the boiler to rest 
upon. 

But with horizontal tubular or water tube boilers the 
matter of brick work becomes important, and partic- 
ular attention should be paid to securing a good foun- 
dation for the walls and great care exercised in building 
them in such manner that the expansion of the inner 
wall or lining will not seriously affect the outer walls. 
This can be done be leaving an air space of two inches 
in the rear and side walls, beginning at or near the 
level of the grate-bars and extending as high as the 
fire line, or about the center line of the boiler. Above 
this height the wall should be solid. Fig. 4 shows a 
plan and an end elevation illustrating this idea. The 
ends of some of the bricks should be allowed to project 
at intervals from the outer' walls across the air space, 
so as to come in touch with the inner walls. 

27 



£8 



ENGINEERING 



Where boilers are set in batteries of two or more the 
middle or party walls should be built up solid from 
the foundation. All parts of the walls with which the 





FIGURE 4. 

fire comes in contact should be lined with fire brick, 
every fifth course being a header to tie the lining to 
the main wall. 

Bridge walls should be built straight across from 
wall to wall of the setting, and should not be curved to 
conform to the circle of the boiler shell. The proper 



-4^ 




FIGURE 5. 



distance from the top of the bridge wall to the bottom 
of the boiler varies from eight to ten inches, depend- 
ing upon the size of the boiler. The space back of the 



BOILER SETTINGS AND APPURTENANCES 



29 



bridge wall, called the combustion chamber, can be 
filled in with earth or sand, and should slope gradually 
downward from the back of the bridge wall to the floor 
level at the rear wall, and should be paved with hard 
burned brick. The ashes and soot can then be easily 
cleaned out by means of a long-handled hoe or scraper 
inserted through the cleaning out door, which should 
always be placed in the back wall of every boiler set- 
ting. 

Back Arches. A good and durable arch can be made 







FIGURE 6. 



for the back connection, extending from the back wall 
to the boiler head, by taking flat bars of iron ^ x 4 in., 
cutting them to the proper length and bending them 
in the shape of an arch, turning four inches of each 
end back at right angles, as shown in Fig. 5. The 
distance 0-B should equal that from the rear wall to 
the boiler head, and the height, O-A, should be about 
equal to O-B, and should bring the point A about two 
inches above the top row of tubes. The clamp thus 
formed is filled with a course of side arch fire brick, 



30 



ENGINEERING 



Fig. 6, and will form a complete and self-sustaining 
arch, the bottom, B, resting on the back wall, and the 
top, A, supported by an angle iron riveted across the 
boiler head about three inches above the top row of 
tubes. See Figs. 7 and 8. 

Enough of these arches should be made so that when 
laid side by side they will cover the distance from one 
side wall to the other across the rear end of the boiler. 
A fifty-four-inch boiler would thus require six clamps, 




FIGURE {, 



a sixty-inch boiler seven clamps, and a seventy-two- 
inch boiler would require eight clamps; the length of 
a fire brick being about nine inches. In case of needed 
repairs to the back end of the boiler the sections can 
be lifted off, thus giving free access to all parts, and 
when the repairs are completed the arches can be reset 
with very little trouble and much less expense than the 
building of a solid arch would necessitate. This form 
of segmental arch allows ample freedom for expansion 



BOILER SETl^lNGS AND APPURTENANCES 



31 



of the boiler, in the direction of its length, without 
leaving an opening when the boiler contracts. 

The crosswise construction of arch bars, while afford- 
ing equal facility in repair work, is necessarily more 
expensive than the form here described, and is also 
open to the objection that it cannot follow the con- 
tracting boiler and maintain a tight joint or connection 




FIGURE 8. 



between the back arch and the rear head above the 
tubes. 

Boiler walls should always be well secured in both 
directions by tie rods extending throughout the entire 
length and breadth of the setting, wnether there be one 
boiler or a battery of several. The bottom rods 
should be laid in place at the floor level when starting 
the brick work, and the top rods extending transversely 
across the boilers can be laid on top of the boilers. 



32 ENGINEERING 

The top rods extending from front to back can be laid 
in the side walls or rest on top of them. All tie rods 
should be at least one inch in diameter, and for batter- 
ies of several boilers they should be larger. The rods 
, i.ould extend three or four inches beyond the brick 
work, with good threads and nuts on each end to 
receive the buck stays. In laying down the transverse 
tie rods they should be located so as to allow the buck 
stays to bind the brick work where the greatest con- 
centration of heat occurs. 

Horizontal boilers should always be set at least one 
inch lower at the back end than at the front, to make 
sure that the rear ends of the tubes will be covered 
with water so long as any appears in the gauge glass, 
provided of course that the lower end of the glass is 
properly located with reference to the top row of 
tubes, which will be discussed later on. Upon the 
brick work and immediately under each lug of the 
boiler there should be laid in mortar a wrought or cast 
iron plate several inches larger in dimension than the 
bearing surface of the lug and not less than one inch in 
thickness. Upon each of these plates there should be 
placed two rollers made of round iron i or i}i in. in 
diameter, and as long as the width of the lug. These 
rollers should be placed at right angles to the length 
of the boiler, in such a position that the lug will bear 
equally upon them. The object of the rollers is to 
prevent disturbance of the brick work by the endwise 
expansion and contraction of the boiler. 

Grate Surface. The number of square feet of grate 
surface required depends upon the size of the boiler. 
A good rule and one easy to remember is to make the 
length of the grates equal to the diameter of the boiler. 
The width, of course, will depend upon the construe* 



BOILER SETTINGS AND APPURTENANCES 33 

tion of the furnace. If the fire brick lining is built 
perpendicular, the width of grate will be about equal 
to the diameter of the boiler. On the other hand, if 
the lining is given a batter of three inches, starting at 
the level of the grate, then the width will be reduced 
(six inches. It is customary to allow one square foot 
of grate surface to every 36 sq. ft. of heating surface. 
The distance of the grate-bars from the shell of the 
boiler varies from 24 to 28 in., according to the dimen- 
sions of the boiler. 

Insulation. All boilers should be well protected 
from the cooling influence of outside air, if economy 




M CLAVE' S GRATES. 



of fuel is any object. The tops of horizontal boilers 
should be covered with some kind of heat insulating 
material, or arched over with common brick, leaving a 
space of two inches between the boiler and the arch. 
The resulting saving in fuel will far more than com- 
pensate for the extra expense in a very short time. 
All cracks in the side and rear walls should be care- 
fully pointed up with mortar or fire clay. One source 
of heat loss in return flue boilers is short circuiting 
from the furnace to the breeching, caused by the 
arches over the fire doors becoming loose and shaky, 
and allowing considerable of the heat to escape directly 
to the stack instead of passing under the boiler and 



34 ENGINEERING 

through the tubes. Another bad air leak ofton occurs 
at the back connection when the arch rests wholly 
upon iron bars imbedded in the side walls. This leak, 
as has already been noted, is caused by the expansion 
of the boiler, which gradually pushes the arch away 
from the back head until, in the course of time, there 
will be a space of ^ in. and sometimes % in. between 
the head and the arch. The obvious remedy for this 
is an arch that will go and come with the movement 
of the boiler, and such an arch can be secured by build- 
ing it in sections, as illustrated by Fig. 3, and then 
riveting a piece of angle iron to the boiler head, above 




M' CLAVE S GRATES. 



the top row of tubes for the upper ends of the sections 
to rest upon, as already described. It will be seen 
that within all possible range of boiler movement in 
either direction the arch will, with this construction, 
always remain close to the head. 

Water Columns. Water columns should be so located 
as to bring the lower end of the gauge glass exactly on 
a level with the top of the upper row of tubes, thus 
always affording a perfect guide as to the depth of 
water over the tubes. Many gauge glasses are placed 
too low, and water tenders and firemen are often 
deceived by them unless their positions with relation to 
the tubes are carefully noted 



BOILER SEITINGS AND APPURTENANCES 35 

The only safe plan for an engineer to pursue in 
taking charge of a steam plant is to seize the first 
opportunity for noting this relation. When he has 
washed out his boilers he may leave the top man-hole 
plates out while refilling them, and when the water 
stands at about four inches over the top row of tubes, 
the depth of water in the glass should be measured. 
He should do this with every boiler in the plant, and 
make a memorandum for each boiler. He will then 
know his bearings with regard to the safe height of 
water to be carried in the several gauge glasses. If he 
finds any of them are too low, he should lose no time 




M' clave' S GRATES. 

in having them altered to comform to the requirements 
of safety. The position of the lower gauge cock 
should be three inches above the top row of tubes. 

In making connections for the water column plugged 
crosses should always be used in place of ells. Brass 
plugs are to be preferred if they can be obtained; but 
whether of brass or iron, they should always be well 
coated with a paste made of graphite and cylinder oil 
before they are screwed in. They can then be easily re- 
moved when washing out the boiler, so as to allow the 
scale, which is sure to form in the lower connection, to 
be cleaned out. The best point at which to connect the 
lower pipe with the boiler is in the lower part of the 



36 ENGINEERING 

head just below the bottom row of tubes, and near the 
side of the boiler on which the water column is to 
stand; ij< or i>^ in. pipe should be used in all cases. 
The top connection can be made either in the head 
near the top, or in the shell. A ^ or i in. drain pipe 
should be led into ^he ash pit, fitted with a good reli- 




AUXILIARY SPRING PRESSURE GAUGE, 

able valve which should be opened at frequent intervals 
to allow the mud and dirt to blow out of the water col- 
umn and its connections. This is a very important 
point, and great care should be taken to keep the 
water column and all its connections thoroughly clean 
at all times. 

One of the best indications that some portion of the 



BOILER SETTINGS AND APPURTENANCES 37 

connections between the water glass and the boiler is 
choked or plugged with scale, is when there is no per- 
ceptible movement of the water in the glass. When 
the connections are free and the boiler is being fired, 



AUXILIARY SPRING PRESSURE GAUGE, SECTIONAL VIEW. 

there is always a slight movement of the water up and 
down in the glass, and when there is no perceptible 
movement it is time to look for the cause at once. 
Many instances of burned tubes have occurred, and 



38 



ENGINEERING 



even explosions caused by low water in boilers while 
the gauge glass showed the water to be at a safe 
height. But owing to the connections having become 
plugged with scale, the water in the glass had no con- 
nection whatever with that in the boiler, and the water 
column was therefore worse than useless. 




Steam Gauges. As water columns are made at pres- 
ent the steam gauge is usually connected at the top of 
the column. This makes a handsome and convenient 
connection, although theoretically the proper method 
would be to connect the steam gauge directly with the 
dome or the steam space of the shell. There should 
always be a trap or siphon in the gauge pipe in order 



BOILER SETTINGS AND APPURTENANCES 39 

to retain the water of condensation, so as to prevent 
the hot steam from coming in contact with the spring. 
If at any time the water is drained from the siphon, 
care should be exercised in turning on the steam 
again by allowing it to flow in very slowly at first until 
the siphon is again filled with water. 

The steam gauge and the safety valve should be com- 
pared frequently by raising the steam pressure high 
enough to cause the valve to open at the point for 
which it is set to blow. 

Safety Valves. The modern pop valve is generally 
reliable, but, like everything else, if it is allowed to 
stand idle too long it is likely to become rusty and 
stick. Therefore it should be allowed to blow off at 
least once or twice a week in order to keep it in good 
condition. 

Most pop valves for stationary boilers are provided 
with a short lever, and if at any time the valve does 
not pop when the steam gauge shows the pressure to 
be high enough, it can generally be started by a light 
blow on the lever with a hammer. 

The ratio of safety valve area to that of grate surface 
is, for the old style lever and weight valve, i sq. in. of 
valve area for each 2 sq. ft. of grate surface, and 
for pop valves i sq. in. of valve area for each 3 sq. ft, 
of grate surface. 

Each boiler in a battery should have its own safety 
valve, and, in fact, be entirely independent of its mates 
as regards safety appliances. 

One example of safety valve computation will be 
given. Suppose the grate surface of a boiler is 
Sy6 = 30sq. ft, what should be the diameter of the 
lever safety valve? The required area of the valve is 
30-^2=15 sq. in. Then 15-^.7854=19, which is the 



40 ENGINEERING 

square of the diameter of the valve. Extracting the 
square root of 19 gives 4.35 in. diameter of valve. In 
actual practice one 5 in. or two 3 in. lever safety 
valves would be required. If a pop valve is to be used 
the required area is 30- 3 = 10 sq. in. Then 10 -^ .7854 = 
12.73 = square of diameter of valve. Extract the 



POP VALVE. 



square root of 12.73 and the result is 3.6 in. = diam- 
eter of valve. In practice a 4 in. valve would be 
required. 

Fusible Plugs. A fusible plug should be inserted in 
that part of the heating surface of a boiler which is 
first liable to be overheated from lack of water. 



BOILER SETTINGS AND APPURTENANCES 



41 



In a horizontal tubular or return flue boiler the 
proper location for the fusible plug is in the back heaa 




INSIDE VIEW OF A POP SAFETY VALVE. 

about lj4 or 2 in. above the top row of tubes. In nre- 
box Doilers the plug can be put into the crown sheet 



4:2 ENGINEERING 

flciirectly over the fire. These plugs should be made of 
^brass with hexagon heads and standard pipe threads, 
in sizes J^, ^, i in., or even larger if desired. A hole 
driiied axially through the center and counter sunk in 
the end chat enters the boiler is filled with an alloy of 
such composition that it will melt and run out at the 
temperature of the dry steam at the pressure carried 
in the boiler. Thus, if the water should get below the 
plug the dry steam, coming in contact with the fusible 
alloy, melts it and, escaping through the hole in the 
plug, gives the alarm, and in case of fire-box or inter- 
nally fired boilers the steam will generally extinguish 
the fire also. The hole is counter sunk on the inner 
end of the plug so as to retain the fusible metal against 
the boiler pressure. These plugs should be looked 
after each time the boilers are washed out, and all dirt 
and scale should be cleaned off in order that the fusible 
metal may be exposed to the heat. 

Another type of fusible plug consists of a small brass 
cylinder into one end of which is screwed a plug filled 
with a metal which will fuse at the temperature of dry 
steam at the pressure which is to be carried in the 
boiler. The other end of the cylinder is reduced and 
fitted with a small stop valve and threaded to screw 
into a brass bushing inserted into the top of the boiler 
shell. This bushing also receives at its lower end a 
piece of y^ or ^4 in. pipe which extends downwards to 
within 2 in. of the top row of tubes, or the crown sheet 
if the boiler is internally fired. The principle of the 
ievice is that in case the water falls below the lower 
-end of the pipe, steam will enter, fuse the metal in the 
T)lug, and be free to blow and give warning of danger. 
Some of these appliances are fitted with whistles 
which are sounded in case the steam g-ets access to 



BOILER SETTINGS AND APPURTENANCES 43 

them. But even with such devices no engineer can 
afford to relax his own vigilance and depend entirely 
upon the safety appliances to prevent accidents from 
low water. 

Domes and Mud-Drums. As a general proposition, 
both mud drums and domes are useless appendages to 
steam boilers. There are, no doubt, instances where 
they may serve a purpose, but as a rule their use is of 
no advantage to a boiler. Neither are the so-called 
circulating systems, sometimes attached to return 
tubular boilers, of any real value. These consist of 
one or more 4106 in. pipes extending under the boiler 
from front to back through the furnace and the com- 
bustion chamber and connected to each end of the 
boiler. 

Feed Pipes. Authorities differ in regard to the 
proper location of the inlet for the feed pipe, but 
upon one point all are agreed, namely, that the feed 
water, which is always at a lower temperature than the 
water in the boiler, should not be allowed to come 
directly in contact with the hot boiler sheets until its 
temperature has been raised to within a few degrees of 
the temperature of the water in the boiler. Cer- 
tainly one of the most fruitful sources of leaks in the 
seams and around the rivets is the practice of intro- 
ducing the feed water into the bottom either at the 
back or front ends of boilers, as is too often the case. 
The cool water coming directly in contact with the hot 
sheets causes alternate contraction and expansion, and 
results in leaks, and very often in small cracks in the 
sheet, the cracks extending radially from ihe rivet 
holes. It would appear that the proper method is to 
connect the feed pipe either into the front head just 
above the tubes, or into the top of the shell. The 



44 ENGINEERING 

nipple entering the boiler should have a long thread 
cut on the end which screws into the sheet, and to this 
end inside the boiler there should be connected another 
pipe which shall extend horizontally at least two- 
thirds of the length of the boiler, resting on top of the 
tubes, and then discharge. Or, what is still better^ 
allow the internal pipe to extend from the entering 
nipple at the front end to within a few inches of the 
back head, then at right angles across the top of the 
tubes to the other side, and from there discharge 
downward. By this method the feed water is heated 
to nearly, if not quite, the temperature of the water in 
the boiler before it is discharged. One of the objec- 
tions to this system is the liability of the pipe inside 
the boiler to become filled with scale and finally 
plugged entirely. In such cases the only remedy is to 
replace it with new pipe. But the great advantage of 
having the water thoroughly heated before being dis- 
charged into the boiler will much more than compen- 
sate for the extra expense of piping, and the general 
idea of introducing the feed water at the top instead of 
at the bottom of the boiler is therefore recommended 
as being the best. 

The diameter of feed pipes ranges from i in. for 
small sized boilers, up to lyi and 2 in. for boilers of 54 
to 'J2 in. in diameter. It is not good policy to have 
the feed pipe larger than necessary for the capacity of 
the boiler; because it then acts as a sort of cooling 
reservoir for the feed water, and may cause considerable 
loss of heat. 

For batteries of two or more boilers it is necessary to 
run a main feed header, with branch pipes leading to 
each boiler. The header should be large enough to 
supply all the boilers at the same time, should it ever 



BOILER SETTINGS AND APPURTENANCES 45 

become necessary to do so. The header can be run 
along the front of the boilers just above the fire doors 
with the branch pipes running up on either side, clear 
of the flue doors and entering the front connection, or 
smoke arch, and the boiler head at a point two inches 
above the tubes. There should always be a valve in 
each branch pipe between the check valve and the 
header for the purpose of regulating the supply of 
water to each boiler, and also for shutting off the 
pump pressure in case of needed repairs to the check 
valve. Another valve should be placed between the 
check valve and the boiler. By this arrangement it is 
always possible to get at the check valve when it is 
out of order. 

Blow off Pipes. Blow off pipes should always be 
connected with the lowest part of the water space of a 
boiler. If there is a mud-drum, then of course the 
blow off should be connected with it; but if there is no 
mud-drum, the blow off should connect with the bot- 
tom of the shell, near the back head, extend down- 
wards to the floor of the combustion chamber, and 
thence horizontally out through the back wall, where 
the blow off cock can be located. 

The best blow off cocks are the asbestos packed 
iron-body plug cocks, which are durable and safe. 
A globe valve should never be used in a blow off pipe, 
because the scale and dirt will lodge in it and prevent 
its being closed tightly. A straight way or gate valve 
is not so bad, but an asbestos packed plug cock is 
undoubtedly the best and safest. 

In order to protect the blow off pipe from the 
intense heat, a shield consisting of a piete of larger 
pipe can be slipped over the vertical part before it is 
connected. 



46 



ENGINEERING 



Blow off cocks should be opened for a few seconds 
once or twice a day, to allow the scale and mud to be 
blown out. If neglected too long they are liable to 
become filled with scale and burn out. A plan which 
is said to give good results is to connect a tee in the 
horizontal part of the pipe, and from this tee run a i in. 




FIGURE 9. 

pipe to a point in the back head at the water level. 
It is claimed that this will cause a circulation of water 
in the pipe and prevent the formation of scale. 

A surface blow off is a great advantage, especially 
if the water is muddy or liable to foam. By having 
the surface blow off connected on a level with the 



BOILER SETTINGS AND APPURTENANCES 47 

water line a large amount of mud and other matter 
which is kept on the surface by the constant ebullition 
can be blown out. 

A combination surface blow off, bottom blow off, 
and circulating system can be arranged by a connec- 
tion such as illustrated in Fig. 9. By closing cock A 
and opening cocks B and C the bottom blow off is put 
in operation; by closing B and opening A and C the sur- 
face blow off is started, and by closing C and leaving 
A and B open the device will act as a circulating sys- 
tem. The pipe should be of the same size throughout. 
Blow off pipes should be of ample size, never less than 
i}( in., and from that to 2^ in., depending upon the 
size of the boiler. 

Feed Pumps and Injectors. The belt driven power 
pump is the most economical boiler feeder, but is not 



DIFFERENTIAL VALVE, DAVIS PUMP. 

the most convenient nor the safest. When the engine 
stops, the pump stops also, and sometimes it happens 
that the belt gives way and the pump stops at iust 



48 



ENGINEERING 



the time when the boiler is being worked the hard- 
est. 

The modern double acting steam pump, of which 
there are many different makes to choose from, is 
without doubt the most reliable boiler feeding appli- 
ance and the one best adapted to all circumstances 
and conditions, although it is not economical in the 




DAVIS BELT DRIVEN FEED PUMP. 



use of steam, since the principle of expansion cannot 
be carried out with the pump as with the engine. 

In selecting a feed pump care should be exercised to 
see that it is of the proper size and capacity to supply 
the maximum quantity of water that the boiler car 
evaporate. This may be ascertained by taking intr 
consideration the amount of heating surface and the 
required consumption of coal per square foot of grate 
suiface per hour. First, take the coal consumption. 
Assume the boiler to have 30 sq. ft. of grate surface, 



BOILER SETTINGS AND APPURTENANCES 



49 



and that it is desired to burn 15 lbs. of coal per square 
foot of grate per hour, which is a good average with 
the ordinary hand fired furnace using bituminoui coal. 




SECTIONAL VIEW OF DIFFERENTIAL VALVE. 

Suppose the boiler is capable of evaporating 8 lbs. of 
water per pound of coal consumed. Then 30 x 15x8 = 
3,600 lbs. of water evaporated per hour. Dividing 




WORTHINGTON DUPLEX BOILER FEED PUMP. 

3,600 by 62.4 (the weight of a cubic foot of water in 
pounds) gives 57.6 cu. ft. per hour, which, divided by 
60, gives 0.96 cu. ft. per minute. This multiplied by 



50 



ENGINEERING 



1,728 ( number of cubic inches in a cubic foot) give« 
1,659 cu. in. per minute which the pump is required to 
supply. Suppose the pump is to make forty strokes 
per minute, and the length of stroke is five inches. 
Then 1659 -^40 = 41.47 cu. in. per stroke, which, divided 
by 5 (length of stroke in inches) gives 8.294 sq. in. as 
the required area of water piston. 8.294 -j- ,7854 = 
10.56, which is the square of the corresponding diam- 







PHANTOM VIEW OF MARSH INDEPENDENT STEAM PUMP. 



eter, and the square root of 10.56 = 3.25. So, theo- 
retically, the size of the water end of the pump would 
be 3^ in. in diameter by 5 in. stroke; but as it is 
always safer to have a reserve of pumping capacity, 
the proper size of the pump would be 3>^ in. in diam- 
eter by 5 in. stroke, with a steam cylinder of 6 or 7 in. 
in diameter. 

There is another rule for ascertaining the size of the 



BOILER SETTINGS AND APPURTENANCES 



51 



feed pump, by taking the number of . juare feet of 
heating surface in the boiler and allow a pump capacity 
of I cu. ft. per hour for each 15 sq. ft of heating sur- 
face. Thus, let the total heating surface of the boiler 
be 786 sq. ft. Dividing this by 15 gives 52.4 as the 
number of cubic feet of water required per hour, from 
which the pump dimensions may be found in the same 
way as in the preceding case. 

In figuring on the capacity of a feed pump for a bat- 
tery of two or more boilers, the total quantity of wate^* 
required by all the boilers 
must be taken into consid- 
eration. All boiler-rooms 
should be supplied with at 
least two feed pumps, so 
that if one breaks down 
there may always be an- 
other one available. 

The injector is a reliable 
boiler feeder, and is in fact 
more economical than the 
steam pump, because the 
heat in the steam used is 
all returned to the boiler, 

excepting the losses by radiation. But the disad- 
vantage attending the use of the injector is that it will 
not work well with the feed water at a temperature 
very much in excess of 100° F. , while a good steam 
pump, fitted with hard rubber valves, will handle watei 
at a temperature as high as 200° or 208^ F., when the 
water flows to the pump by gravity from a heater, 01 
it will raise water from a receiving tank on a short 
suction lift at a temperature of 150° or 160° F. 

Feed Water Heaters. One great source of economy 




U. S. AUTOMATIC INJECTOR, 



52 



ENGINEERING 



in fuel is the utilization of all the available exhaust 
steam for heating the feed water before it enters the 
boiler. Of course if the main engine is a condensing 
engine, the exhaust from that source is not directly 
available, except by interposing a closed heater 
between the cylinder and the condenser, or by using 




METROPOLITAN INJECTOR, MODEL O. 



the water of condensation for feeding the boilers. 
This can be done with safety, provided a surface con- 
denser is used, but with a jet condenser or an open 
heater in which the exhaust mingles with the water, it 
is advisable to have an oil separator to prevent the oil 
trom getting into the boilers. 



BOILER SETTINGS AND APPURTENANCES 



53 



Exhaust heateis are of two kinds, open and closed. 
In the open heater the exhaust steam mingles directly 
with the water and a portion of it is condensed. A 
well-designed open exhaust heater will raise the tem- 
perature of the water to very 
nearly the boiling point, 212^^ 
F. These heaters should be 
set so that the water w^ill flow 
by gravity from them to the 
feed pump In the closed type 
of exhaust heaters, the exhaust 
steam and the water are kept 
separate. In some styles the 
steam passes through tubes, 
which are surrounded by water, 
while in others the water fills 
the tubes, which are in turn 
surrounded by the steam. In 
either case the water in the 
closed heater is under the full 
boiler pressure while the feed 
pump is in operation, because 
the heater is between the pump 
and the boiler, while with the 
open heater the pump is be- 
tween the heater and the boiler. 

The saving effected by heat- 
ing the feed water with exhaust 
steam can be easily ascertained 
by the use of a thermometer, 

a steam table, and a simple arithmetical calcula- 
tion. First, find by thermometer the temperature 
of the water before entering the heater; find its tem- 
perature as it leaves the heater. Next ascertain by 




yiiiiiuni 

JiiiiflvMllH-iM« 



BARAGWANATH STEAM 

JACKET FEED WATER 

HEATER. 



54 



ENGINEERING 



the steam table the number of heat units above 32° 
F. in the water at each of the two temperatures. Sub- 
tract the less from the greater, and the remainder will 
be the number of heat units added to the water by the 
heater. Next find by the table the number of heat 

units above 32° F. in the steam 
at the pressure ordinarily car- 
ried in the boiler, and subtract 
from this the number of heat 
units in the water before it 
enters the heater. The result 
will be the number of heat 
IPiliii units that would be required to 
convert the water into steam of 
the required pressure, provided 
no heater were used. Then to 
BiSiSiSili| the percentage of saving 

ii^Hlllllii^H^'^ effected by the heater, multiply 
^^^^ the number of heat units added 
IlljIiJ to the water by the heater by 
QiaH 100, and divide by the number 
of heat units required to con- 
vert the unheated water into 
iPilllilil steam, from the initial temper- 
ature at which it enters the 
|H:.^ ' -^-'vvi heater. 

^ Example. Assume the boiler 

INTEuiun viii;vv Oi?' OPEN ^ , 

HEATER. to be carry mg 100 lbs. gauge 

pressure. Suppose the temper- 
ature of the water before entering the heater is 
60° F. , and that after leaving the heater its tem- 
perature is 202° F. , what is the percentage of saving 
due to the heater? The solution of the problem is as 
follows: 




BOILER SETTINGS AND APPURTENANCES 55 




SQUARE OPEN HEATER. 



56 ENGINEERING 

Boiler pressure by gauge = lOO lbs. 

Initial temperature of feed water = 60° F. 

Heated temperature of feed water = 202° F. 

From the steam table (see Chapter IV., Table 5) it 
is found that 

Heat units in water at 202° F. = 170.7. 

Heat units in water at 60^ F. = 28.01. 

Heat units added to water by heater = 170.7 — 28.01 = 
142.69. 

Heat units in steam at 100 lbs. gauge pressure = 
1 185.0. 

Heat units to be added to water at 60° F. to make 
steam of 100 lbs. gauge pressure = 1185.0 — 28.01 = 
1156.99. 

Percentage of saving effected by the use of the 

, ^ 142.69 X 100 

heater = ^ =12.33 P^^ cent. 

1156.99 -^^ ^ 

Suppose the coal consumed under this boiler amounts 
to two tons per day at a cost of $3.00 per ton, or a fuel 
cost of S6.00 per day. Then the saving in dollars and 
cents due to the heater in the foregoing example would 
be 12.33 per cent of ^6.00, or $0.7398 (74 cents) per 
day. 

Heaters, especially those of the closed type, should 
have capacity sufficient to supply the boiler for fifteen 
or twenty minutes. There would then be a body of 
water continually in the heater in direct contact with 
the heating surface, and as it passes slowly through it 
will receive much more heat rhan if rushed through a 
heater that is too small. All heaters and feed pipes 
should be well protected by some good insulating 
covering to prevent loss of heat by radiation. In 
some cases the exhaust steam, or a portion of it at 
least, can be used to advantage in an exhaust injector. 



BOILER SETTINGS AND APPURTENANCES 



57 



This device, where it can be used at all, is economical 
in that it not only feeds the boiler, but also heats the 




CLOSED FEED WATER HEATER. 

water without the use of live steam. But it will not 
force (he water against a pressure much above 75 lbs. 



58 ENGINEERING 

to the square inch, and if the initial temperature of 
the water is much above 75° F. the exhaust injector 
will not handle it. Heaters which use live steam 
direct from the boilers heat the feed water to a much 
higher temperature, so that they act as purifiers by 
removing a large portion of the scale-forming impu- 
rities before the water enters the boiler. Live steam 
heaters, however, are not to be considered as econo- 
mizers of heat. 

Provisions for Testing. While considering feed pipes 
and other apparatus necessarily appercaining to the 
feeding of boilers, it is well to devote a short space 
also to the fittings and other devices required for suc- 
cessfully conducting tests of the boiler and furnace. 
This subject is mentioned here for the reason that the 
author considers that the necessary fittings and appli- 
ances for making evaporative tests properly belong to, 
and in fact are a part of, the feed piping, and can be 
put in while the plant is being erected at much less 
cost and trouble than if the matter is postponed until 
after the plant is in operation. 

Beginning then at the check valve, there should be a 
tee located in the horizontal section of the feed pipe, 
as near to the check valve as^ practicable, and between 
it and the feed pump; or a tee can be used in place of 
an ell to connect the vertical and horizontal sections 
of the branch pipe where it rises in front of the boiler. 
One opening of this tee is reduced to ^ or ^ in. to 
permit the attachment of a hot water thermometer. 
These thermometers are also made angle-shaped at the 
* shank, so that if desired they can be screwed into a tee 
placed in vertical pipe and still allow the scale to 
stand vertical. The thermometer is for the purpose 
of showing at w^hat temperature the feed water enters 



BOILER SETTINGS AND APPURTENANCES 



59 



the boiler during the test, and there- 
fore should be as near the boiler as 
possible. After the test is completed 
the thermometer may be taken out 
and a plug inserted in its place. 

The next requirement will be a de- 
vice of some kind for ascertaining the 
weight of water pumped into the 
boiler during the test. In some well 
ordered plants each boiler is fitted 
with a hot water meter in the feed 
pipe, but as this arrangement is hardly 
within the reach of all, a substitute 
equally as accurate can be made by 
placing two small water tanks, each 
having a capacity of eight or ten cubic 
feet, in the vicinity of the feed pump. 
These tanks can be made of light 
tank iron, and each should be fitted 
with a nipple and valve near the bot- 
tom for connection with the suction 
side of the pump. The tops of the 
tanks may be left open. If an open 
heater is used, and it is possible to 
place the tanks low enough to allow 
a portion of the water from the heater 
to be led into them by gravity, it will 
be desirable to do so. A pipe leading 
from the main water supply, with a 
branch to each tank, is also needed 
for filling them. One of the feed hot water ther- 

r u • 1^ j.i_ 1- 1 J 1 MOMETER. 

pumps, or which there should always 

be at least two, as already stated, is fitted with a tee 

in the suction pipe near the pump to receive the pipe 



60 



ENGINEERING 



leading from the tanks. During the test the main suc- 
tion leading to this pump from the general supply 
should be kept closed, so that only the water that 
passes through the tanks is used for feeding the boiler. 
If the plant be a small one, with but one or two boil- 
ers and only a single feed pump, the latter can be 
made to do duty as a testing pump, because during 
the test there will be no other boilers to feed besides 
the ones under test. 



c — ^ ^ 



Si/ppiy 




TOP'^PPUMP 



FIGURE 10. 



If metal tanks are considered too expensive, two 
good water-tight barrels can be substituted. Fig. lo 
will give the reader a general idea of what is needed 
for obtaining the weight of the water by the method 
just described. If a closed heater is used and no other 
boilers are in service during the test, the cold water 
can be measured in the tanks and pumped directly 
through the heater, but if it is necessary to feed other 
boilers besides those under test, then either a separate 



BOILER SETTINGS AND APPURTENANCES 61 

feed pipe must be run to the test boileis, or else hot 
water meters will have to be put into the branch pipes. 

In cases where a separate feed pipe must be put in 
for the test boiler and the water which is used for 
testing cannot be passed through a heater, there 
should be a ^4 or i in. pipe connected to the feed main 
or header and leading to the testing tanks, in order to 
allow a portion of the hot feed w^ater to run into and 
mix with the cold water in the tanks as they are being 
filled, thus partially warming the water before it goes 
to the boiler. 

Heating Surface. The heating surface of a boiler 
consists of that portion of the boiler which is exposed 
to the heat on one side and water on the other. In a 
horizontal boiler of either the flue or tubular type, the 
available heating surface is, first, the lower half of the 
shell; second, the area of the back head below the 
water line minus the combined cross sectional area of 
all the tubes or flues; third, the inside area of the 
flues; fourth, the area of the front head minus the sec- 
tional area of the flues. 

For a fire-box boiler of the vertical type, the area of 
the flue sheets minus the sectional area of the flues, 
plus the area of the fire-box plus the inside area of the 
flues constitutes the heating surface. If the boiler is a 
horizontal internally fired boiler, the heating surface 
will consist of, first, area of three sides of the fire- 
box; second, area of the crown sheet; third, area of 
flue sheets minus sectional area of flues; fourth, inside 
area of the flues. 

In estimating the area of the fire-box, the area of the 
fire door should be subtracted therefrom. If the fire- 
box be circular, as in the case of a vertical boiler, the 
area may be obtained by first finding by measurements 



b)Z ENGINEERING 

the diameter, which multiplied by 3.1416 will give the 
circumference. Then multiply this result by the 
height or the distance between the grate bars and 
the flue sheet. In the case of water tube boilers the 
outside area of the tubes must be taken. Two exam- 
ples will be given illustrating methods of calculating 
heating surface: 

First, take a horizontal tubular boiler, diameter ^2 
in., length 18 ft., having sixty-two 4}4 in. flues; find 
area of lower half of shell. 

Circumference = diameter x 3.1416 = 18.8496 ft. 

One-half of the circumference multiplied by the 
length = required area. Thus, 18.8496 h- 2 x 18 = 169.64 
sq. ft. 

Next find heating surface of back head below the 
water line. Total area = 72^ x .7854 = 4071.5 sq. in. 
Assume two-thirds of this area to be exposed to the 
heat, ys of 4071.5 = 2714.3 sq. in. From this must be 
deducted the sectional area of the tubes. In giving 
the size of boiler tubes the outside diameter is taken. 
The tubes being 4}4 in.; the area of a circle 4}^ in. in 
diameter is 15.9 sq. in. Number of flues, 62 x 15.9 = 
985.8 sq. in. = sectional area of tubes. The heating 
surface of the back head therefore = 2714.3 — 985.8 = 
1728.5 sq. in. Dividing this by 144, to reduce to feet, 
we have 12 sq. ft. 

Next find inside area of tubes. The standard thick- 
ness of 3. 4}4 in. tube = .134 in. The inside diameter 
therefore will be 4.5 — (2 x .134) = 4.23 in., and the cir- 
cumference will be 4.23x3.1416=13.29 in., and the 
inside area will be 13.29 x length, 18 ft., = 216 in. 
Thus 216 X 13.29 -^ 144 = 19.93 sq. ft., inside area of one 
flue. There being 62 flues, the total heating surface of 
tubes is 19.93x62= 1235.66 sq. ft. The heating sur- 



BOILER SETTINGS AND APPURTENANCES 63 

face of the front head is found in the same manner as 
that of the back head, with the exception that the 
whole area should be figured instead of two-thirds, for 
the reason that the entire surface is exposed to the 
heat, although that portion above the water line may 
be considered as superheating surface. The heating 
surface of front head would be: area 40^^1.5 — sectional 
area of tubes 985.8 = 3085.7 sq. in. = 21.43 sq. ft. 

The total heating surface of the boiler is thus found 
to be 1438.73 sq. ft, divided up as follows 

Lower half of shell, 169.64 sq. ft. 
Back head, 12.00 

Tubes, 1235.66 

Front head, 21.43 

1438.73 

Next taking a vertical fire-box boiler of the follow- 
ing dimensions: diameter of flue sheet, and also of fire- 
box, 50 in.; height of fire-box above grate bars, 30 in.; 
number of flues, 200; size of flues, 2 in.; length of 
flues, 7 ft. 

First, find heating surface in flue sheet. 

Area of circle, 50 in, in diameter = 1,963.5 sq. in. 

Sectional area of 2 in. flue = 3.14 sq. in., which mul- 
tiplied b}^ 200 = 628 sq. in., total sectional area of 
tubes. The heating surface of one flue sheet therefore 
will be 1,963. 5 — 628 ^ 144 = 9 sq. ft. 

Assuming that the tops of the flues are submerged, 
the area of the top flue sheet will also be 9 sq. ft. 
Then heating surface of flue sheets = 9x2= 18 sq. ft. 

Second, find heating surface of tubes. The standard 
thickness of a 2 in. flue is .095 in. The inside diameter 
will consequently be 2 — (.095 x 2) = 1.8 in., and the 
circumference will be 1.8x3.1416=5.66 in. The 



64 ENGINEERING 

length of the flue being 7 ft., or 84 in., the inside area 
will be 5.66 X 84 - 144 = 3.3 sq. ft., and multiplying this 
result by 200 we have 20c x 3.3 = 660 sq. ft. as the 
heating surface of the flues. 

Third, find heating surface of the fire-box. Diam- 
eter of fire-box = 50 in., which multiplied by 
3.1416=157.0^ which is the circumference. The 
height being 30 in., the total area will be 157.08 x 30 -^ 
144 = 32.7 sq. ft. Allowing i sq. ft. as the area of the 
fire door, will leave 31.7 sq. ft. heating surface of fire- 
box. The heating surface of the boiler will be: 

For the flue sheets, 18 sq. ft. 

For the flues, 660 '* 

For the fire-box, 31.7 

Total, 709.7 

The above methods may be applied In estimating the 
heating surface of any boiler, provided in the case of 
water tube boilers that the outside in place of the 
inside area of the tubes be figured. 

Questions 

1. How should the bridge wall of a horizontal boiler 
be built? 

2. How should the brick work of a boiler be secured 
in order to prevent damage by expansion and contrac- 
tion? 

3. Which end of a horizontal boiler should be the 
lowest, and why? 

4. How should the. water column be located? 

5. How high above the top row of tubes should the 
lower gauge cock be? 

6. What is the proper ratio of safety valve area to 
grate surface? 



BOILER SETTINGS AND APPURTENANCES 65 

7. Where should the fusible plug be located? 

8. Where should the feed pipe enter the boiler? 

9. Where should the blow off pipe be connected? 

10. What is the most economical device for feeding 
a boiler? 

11. In selecting a feed pump, how may the requ'^-ed 
size of pump be ascertained? 

12. What is the disadvantage in the use of the 
injector for feeding a boiler? 

13. What is gained by using a feed water heater? 

14. How many kinds of exhaust heaters are there? 

15. How may the saving effected by using the 
exhaust steam for heating the feed water be estimated? 

16. What should the capacity of the heater be? 

17. What provision should be made for testing ';cai 
and other fuel? 

18. What is the heating surface of a boiler? 



CHAPTER III 

BOILER OPERATION 

i^irstcareof the engineer on entering his boiler-room — Cleaning 
fires — Fire tools, etc. — Firing — Suggestions as to best method 
of firing — Quantity of air required per pound of coal — Clean- 
ing tubes — Washing out, etc. — Why it is dangerous to cool a 
boiler too quickly — Repairing tubes — Cleaning inside of 
boiler — Pitting — How to feed a boiler — What to do in cases of 
emergency — Connecting with main — Foaming, priming, etc. — 
Safety valve calculations^ — Rules for safety valve calcula- 
tions—Feed pumps — Care of feed pumps — Directions for set- 
ting steam valves of duplex pumps — Hydraulics for engineers. 

Operation. Having considered in the previous chap- 
ters the principal details in the construction and 
erection of boilers with which the working engineer is 
interested, it is now in order to devote a space to their 
operation. 

Duties, The first act of the careful engineer on 
entering his boiler-room when he goes on duty should 
be to ascertain the exact height of the water in his 
boilers. This he ca i do by opening the valve in the 
drain pipe of the water column, allowing it to blow 
out freely for a few seconds, then close it tight and 
allow the water to settle back in the glass. This 
should be done with each boiler under steam, not only 
once, but several times during the day. No engineer 
should be satisfied with a general squint along the line 
of gauge glasses, but he should either go himself or* 
else instruct his fireman or water tender to make the 
rounds of each boiler and be sure that the water is all 
right. 

66 



BOILER OPERATION 



67 



The next thing to be looked after is the fire. If the 
plant is run continuously day and night it is che duty 
of the firemen coming off watch to have the fires clean, 
the ash pits all cleaned out, a good supply of coal on 
the floor, and everything in good order for the on 
coming force. A good tireman will take pride in 
always leaving things in neat shape for the man who 
is to relieve him. 

Cleaning Fires. With some varieties of coal this is 




LAHMAN S GRATE. 



"^ comparatively easy task, especially if the boilers are 
fitted with shaking grates. With a coal that does not 
form a clinker on the grate bars, the fires can be kept 
in good condition by cleaning them twice or three 
times in twenty-four hours, as the larger part of the 
loose ashes and noncombustible can be gotten rid of 
by shaking the grates and using the slice bar at inter- 
vals more or less frequent; but such coals are generally 
considered too expensive to use in the ordinary manu- 
facturing plant, and cheaper grades are substituted. 



68 



ENGINEERING 



Fire Tools. For cleaning fires successfully and 
quickly the following tools should be provided: a slice 
bar, a fire hook, a heavy iron or steel hoe, and a light 
hoe for cleaning the ash-pit. It is unnecessary to 
describe these tools, as they are familiar to all 
engineers. A suggestion as to the kind of handles 
with which they should be fitted may be of benefit. 
The working ends of the aforesaid tools having been 
made and each welded to a bar of i ox \yi in. round 




MARTIN ANTI-FRICTION ROCKING GRATES. 



iron and lo or 12 in. long, take pieces of i or i^ in. 
iron pipe cut to the length desired for the handles and 
weld the shanks of the tools to them. To the other 
end of the pipe weld a handle made of round iron 
somewhat smaller than the shank. By using pipe 
handles the weight of the tools is considerably lessened, 
and they will still be sufficiently strong. The labor of 
cleaning the fire will thus be greatly lightened. When 
a fire shows signs of being foul and choked with 



BOILER OPERATION 69 

clinker, preparations should be made at once for clean- 
ing it by allowing one side to burn down as low as pos- 
sible, putting fresh coal on the other side alone. When 
the first side has burned as low as it can without 
danger of letting the steam pressure fall too much, 
take the slice bar and run it in along the side of the 
furnace on top of the clinker and back to near the 
bridge wall, then using the door jamb as a fulcrum, give 
it a quick strong sweep across the fire and the greater 
part of the live coals will be pushed over to the other 
'side. What remains of the coal not yet consumed can 
be pulled out upon the floor with the light hoe and 
shoveled to one side, to be thrown back into the 
furnace after the clinker is taken out. Having now 
disposed of the live coal, take the slice bar and run it 
along on top of the grates, loosening and breaking up 
the clinker thoroughly, after which take the heavy hoe 
and pull it all out on the floor. A helper should be 
ready with a pail of water, or, what is still better, a 
small rubber hose connected to a cold water pipe run- 
ning along the boiler fronts for this purpose, and put 
on just enough water to quench the intense heat of the 
red hot clinker as it lies on the floor. When the 
grates are cleaned, close the door, and with the slice 
bar in the other side push all the live coal over to the 
side just cleaned, where it should be leveled off and 
fresh coal added. After this has become ignited, treat 
the other side in the same way. An expert fireman 
will thus clean a fire with very little loss in steam 
pressure, and practically no waste of coal. 

Firing. No definite set of rules for hand firing can 
be laid down that will be suitable for all steam plants, 
or for the many different kinds of coal used. Some 
kinds of coal need very little stirring or slicing, while 



70 ENGINEERING 

others that have a tendency to coke and form a crust 
on top of the fire need to be sliced quite often. 

Every engineer, if he is at all observant, should be 
able to judge for himself as to the best method of 
treating the coal he is using, so as to get the most 
economical results. A few general maxims may be 
laid down. First, keep a clean fire; second, see that 
every square inch of grate surface is covered with a 
good live fire; third, keep a level fire, don't allow hills 
and valleys and yawning chasms to form in the fur- 
nace, but keep the fire level; fourth, when cleaning the 
fire always be sure to clean all the clinkers and dead 
ashes away from the back end of the grates at the 
bridge wall, in order that the air may have a free pas- 
sage through the grate bars, because this is one of the 
best points in the furnace for securing good combus- 
tion provided the bridge wall is kept clean from the 
grates up. By keeping the back ends of the grate bars 
and the face of the bridge wall clean, the air is per- 
mitted to come in contact with the hot fire brick, and 
thus one of the greatest aids to good combustion is 
utilized. Don't allow the fire to become so deep and 
heavy that the air cannot pass up through it, because 
without a good supply of air good combustion is 
impossible. When the chimney draft is good the 
quantity of cold air admitted underneath the grate 
bars may be easily regulated by leaving the ash-pit 
doors partly open. The amount of opening required 
can be ascertained by a little experimenting and 
depends upon the intensity of the draft and the condi- 
tion of the fire. With a clean, light fire and the air 
spaces in the grates free from dead ashes, a slight 
opening of the ash-pit doors will suffice to admit all 
the air required beneath the grates. But if the fire is 



BOILER OPERATION 71 

heavy and the grates are clogged, a larger opening 
will be necessary. In firing bituminous coal contain- 
ing a large percentage of volatile (light or gaseous 
matter) the best results can be obtained by leaving the 
fire doors slightly open for a few seconds immediately 
after throwing in a fresh fire. The reason for doing 
this is that the volatile matter in the coal flashes into 
flame the instant it comes in contact with the heat of 
the furnace, and if a sufficient supply of oxygen is not 
present just at this particular time the combustion will 
be imperfect and the result will be the formation of 
carbon mon-oxide or carbonic oxide gas, and the loss 
of about two-thirds of the heat units contained in the 
coal. This loss can be guarded against in a great 
measure by a sufficient volume of air, either through 
the fire doors directly after putting in a fresh fire, or, 
what is still better, providing air ducts through the 
bridge wall or side walls which will bring the air in on 
top of the fire. Each pound of coal requires for its 
complete combustion 12 lbs. or about 150 cu. ft. of air, 
and the largest volume of air is needed just after fresh 
coal has been added to the fire. 

Cleanliness. In order to get the best results great 
care should be taken that the tubes be kept clean and 
free from soot. Especially does this apply to horizon- 
tal return tubular boilers, for the reason that when the 
tubes become clogged with soot the efficiency of the 
draft is destroyed and the steaming capacity of the 
boiler is greatly reduced. Soot not only stops the 
draft, but it is a non-conductor of heat. In some 
batteries of boilers where an inferior grade of coal is 
used and the draft is poor, it is absolutely necessary 
to scrape or blow the tubes at least once a day in 
order to enable the boilers to generate sufficient steam. 



72 ' ENGINEERING 

As to the process of cleaning there are various 
devices on the market, both for blowing the soot out 
by means of a steam jet and also for scraping the 
inside of the tubes. The steam jet, if properly made 
and used with a high pressure and dry steam, does 
very satisfactory w^ork, but it should not be depended 
upon exclusively to keep the tubes clean, because in 
process of time a scale will form inside the tubes that 
nothing but a good scraper will remove. For that 
reason it is good practice to use the scraper two or 
three times a w^eek at least. When the boiler is 
cooled down for washing out, the bottom of the shell 
should be cleaned of all accumulations of dust and 
ashes, the combustion chamber back of the bridge wall 
cleaned out, and the back flue sheet or head swept off 
and examined, and if there is a fusible plug in the b^ck 
head the scale should be scraped from it, both inside 
and outside the boiler, because if it is covered with 
scale neither the water nor the heat can come in con- 
tact with it, and it will be non-effective. 

Washing Out. The length of time that a boiler can 
be run safely and economically after having been 
washed out depends upon the nature of the feed water. 
If the w^ater is impregnated to a considerable extent 
with scale forming matter, the boiler should be washed 
out every two weeks at the least, and in some cases of 
particularly bad water it becomes necessary to shorten 
the time to one week. To prepare a boiler for washing 
the fire should be allowed to burn as low as possible 
and then be pulled out of the furnace, the furnace 
doors left slightly ajar and the damper left wide open 
in order that the walls may gradually cool. It is as 
bad a practice to cool a boiler off too suddenly as it is 
to fire it up too quick, because the sudden change of 



BOILER OPERATION 73 

temperature either way has an injurious effect on the 
seams, contracting or expanding the plates, according 
as it is cooled or warmed, and thus creating leaks and 
very often small cracks radiating from the rivet holes, 
and becoming larger with each change of temperature, 
until finally the strength of the seam is destroyed and 
rupture takes place. After the boiler has become 
comparatively cool and there is no pressure indicated 
by the steam gauge the blow off cock may be opened 
and the water allowed to run out. The gauge cocks 
and also the drip to the water column should be left 
open to allow the air to enter and displace the water. 
Otherwise there will be a partial vacuum formed in the 
boiler and the water will not run out freely. 

A boiler should not be blown out, that is, emptied 
of water while under pressure. The sudden change of 
temperature is sure to have a bad effect upon the 
sheets and seams. Suppose for instance that all the 
water is blown out of a boiler under a pressure of 
20 lbs. by the steam gauge. The temperature of steam 
at 20 lbs. is 260° F., and it ma}^ be assumed that the 
metal of the boiler is at or near that temperature also. 
Assume the temperature of the atmosphere in the 
boiler-room to be 60° F. There will then be a range 
of 260^ — 60° = 200° temperature for the boiler to pass 
through within a short time, which will certainly have 
a bad effect, and besides this the boiler shell will be so 
hot that the loose mud and sediment left after the 
water has run out is liable to be baked upon the 
sheets, making it much harder to remove. 

While inside the boiler the boiler washer should 
closely examine all the braces and stays, and if any are 
found loose or broken they should be repaired at once 
before the boiler is used again. The soundness of 



74 ENGINEERING 

braces, rivets, etc., can be ascertained by tapping 
them with a light hammer. 

Renewing Tubes, As it is practically impossible to 
prevent scale from forming on the outside of the tubes 
of horizontal tubular boilers unless the feed water is 
exceptionally good, and as the tubes will in course of 
time become leaky where they are expanded into the 
heads, the engineer if he has a battery of two or more, 
should take advantage of the first opportunity that 
presents itself to take out of service the boiler that 
shows the most signs of deterioration and take out the 
tubes, and after cleaning them of scale by scraping and 
hammering or rolling in a tumbling cylinder, he should 
select those that are still in good condition and have 
them pieced out at the ends, making them almost as 
good as new. 

The flues being out of the boiler will give the boiler 
washer a good opportunity to thoroughly clean the 
inside also, and if there are any loose rivets they 
should be replaced and leaky or suspicious looking 
seams chipped and caulked. If there are indications 
of corrosion or pitting, a stiff paste or putty made of 
plumbago mixed with a small proportion of cylinder 
oil may be applied to the affected parts with good 
results. 

Feed Water. There is no steam plant of any conse- 
quence that does not have more or less exhaust steam 
or returns from a steam heating system which can be 
utilized for heating the feed water before it enters the 
boiler. Cold water should never be pumped into a 
boiler that is under steam when it is possible to 
prevent it. 

In feeding a boiler the speed of the feed pump 
should be so gauged as to supply the water just as fast 



ii 



BOILER OPERATION 75 

as it is evaporatea. The firing can then be even and 
regular. 

If the supply of feed water should suddenly be cut 
off, owing to breakage of the pump or bursting of a 
water main, and no other source of supply was avail- 
able, the dampers should be immediately closed, or if 
there should be no damper in the breeching, the draft 
may be stopped by opening the flue doors. The fires 
should then be deadened by shoveling wet or damp 
ashes in on top of them, or if the ashes cannot be 
readily procured, bank the fires over with green coal 
broken into fine bits. This, with the draft all shut off, 
will deaden the fires, while the engine still running 
will gradually use up the extra steam. If the water 
should get dangerously low in the boilers the fires 
may be pulled, provided they have become deadened 
sufficiently, but they should never be pulled while they 
are burning lively, because the stirring will only serve 
to increase the heat and the danger will be aggra- 
vated. 

Connecting a Recently Fired Up Boiler, After a boiler 
has been washed out, filled with water, and fired up, 
the next move is to connect it with the main battery. 
The steam in the boiler to be connected having been 
raised to the same pressure as that in the battery, the 
connecting valve should be opened slightly, just 
enough to permit a small jet of steam to pass through, 
which can be heard by placing the ear near the body of 
the valve. This jet of steam may be passing from the 
battery into the newly connected boiler or vice versa. 
Whichever way it passes, the valve should not be 
opened any farther until the flow of steam stops, 
which will indicate that the pressure has been equal- 
ized. It will then be found that the valve will move 



76 ENGINEERING 

much easier and it may be gradually opened until it is 
.wide open. 

Foaming. Water carried with the steam from the 
boiler to the engine, even if in small quantities, is very 
detrimental to the successful operation of the engine, 
as it washes the oil from the walls of the cylinder, 
thereby increasing the friction, and unless a plentiful 
supply of oil is entering the cylinder cutting of the 
piston rings will take place. There is also danger of 
breaking a cylinder head or of bending the piston rod 
if the water comes in too large quantities. 

There are certain kinds of water which have a natu- 
ral tendency to foam, especially such as contain con- 
siderable organic matter, and the more severe the 
service to which the boiler is put the more will the 
water foam, until it is practically impossible to locate 
the true level of the water in the boilers, and the only 
recourse the water tender has is to keep his feed pump 
running at such a speed as will in his judgment supply 
the water as fast as it goes out of the boilers. It is a 
dangerous condition to say the least, and the only 
remedy for it is either a change to a different kind of 
water, or if this is not possible, then an increase in 
the number of boilers, which would make it possible 
to supply sufficient steam for the engine without being 
compelled to fire the boilers so hard. 

Primi?ig. By which is meant the carrying over of 
water in the form of fine spray mingled with the 
steam, is not so dangerous as foaming and yet it 
causes much loss in the efficiency of a boiler or 
engine. It can be prevented to a large extent by 
placing a baffle plate in the steam space of the boiler 
directly under the dome or outlet to the connection 
with the steam main. 



BOILER OPERATION 77 

Safety Valves. Rules are given in Chapter II. for 
guidance in making calculations relating to spring pop 
valves, which are now almost universally used on 
boilers, and which, without doubt, are the most reliable 
appliance for relieving a boiler of surplus steam. 

A short space will be devoted to the consideration 
of the lever safety valve also, as it may be of interest 
to some students. 

The U. S. marine rule for lever valves is here 
repeated: ''Lever safety valves to be attached to 
marine boilers shall have an area of not less than one 
square inch to every two square feet of grate surface in 
the boiler, and the seats of all such safety valves shall 
have an angle of inclination of 45° to the center line 
of their axis." 

In order to arrive at accurate results in lever safety 
valve calculations it is necessary to know first the num- 
ber of pounds pressure exerted upon the stem of the 
valve by the lever itself, irrespective of the weight, 
also the weight of the valve and stem, as all these 
weights together with the weight of the ball suspended 
upon the lever tend to hold the valve down against 
the pressure of the steam. The effective weight of the 
lever can be ascertained by leaving it in its position 
attached to the fulcrum and connecting a spring bal- 
ance scale to it at the point where it rests on the valve 
stem. The weight of the valve and stem can also be 
found by means of the scale. When the above weights 
are known, together with the weight at the end of the 
lever and its distance from the fulcrum, also the area 
of the valve and its distance from the fulcrum, the 
pressure at which the valve will blow can be found by 
the following rules: 

Rule I. Multipl}^ the weight by its distance from the 



78 ENGINEERING 

fulcrum. Multiply the weight of the valve and lever 
by the distance of the stem from the fulcrum and add 
this to the former product. Divide the sum of the 
two products by the product of the area of the valve 
multiplied by the distance of its stem from the 
fulcrum. The result will be pressure in pounds per 
square inch required to lift the valve. 

Example. Diameter of value, 3 in. 

Distance of stem from fulcrum, 3 in. 

Effective weight of lever, valve and stem, 20 lbs. 

Weight of ball, 50 lbs. 

Distance of ball from fulcrum, 30 in. 

Required pressure at which the valve will blow off, 
50 X 30 + 20 X 3 = 1560. 

Area of valve, 7.0686 x 3 = 21.2058. 

1560- 21.2058 = 73.57 lbs. pressure. 

When the pressure at which it is desired the valve 
should blow off is known, together with the weights of 
all the parts, the proper distance from the fulcrum at 
which to place the weight is ascertained by Rule 2. 

Rule 2. Multiply the area of the valve by the pres- 
sure and from the product subtract the effective weight 
of the valve and lever. Multiply the remainder by the 
distance of the stem from the fulcrum and divide by 
the weight of the ball. The quotient will be the 
required distance. 

Example, Area of valve, 7.07 sq. in. 

To blow off at 75 lbs. 

Effective weight of lever and valve, 20 lbs. 

Weight of ball, 50 lbs. 

Distance of valve stem from fulcrum, 3 in. 

7.07 X 75 --20 = 510.25. 

510.25x3^50 = 30.6 in., distance from fulcrum at 
which to place the ball. 



BOILER OPERATION 79 

When the pressure is known, together with the 
distance of the weight from the fulcrum, the weight of 
the ball is obtained by Rule 3. 

Rule J, Multiply the area of the valve by the pres- 
sure and from the product subtract the effective weight 
of the lever and valve. Multiply the remainder by 
the distance of the stem from the fulcrum and divide 
by the distance of the ball from the fulcrum. The 
quotient will be the required weight. 

Example. Area of valve, . . . . 7.07 sq. in. 

Pressure in pounds per square inch, . . 80 lbs. 

Effective weight of lever and valve, . . 20 lbs. 

Distance of stem from fulcrum, .... 3 in. 

Distance of weight from fulcrum, ... 30 in. 

7.07 X 80-20 = 545.6. 

545.6 X 3 -^ 30 = 54.56 lbs., weight of ball. 

Safety valves, especially those of the lever type, are 
liable to become corroded and stick to their seats if 
allowed to go any great length of time without blow- 
ing. Therefore it is good practice to raise the steam 
pressure to the blowing off point at least two or three 
times a week, or oftener, for the purpose of testing 
the valve. If it opens and releases the steam at the 
proper point all is well, but if it does not, it should be 
looked after forthwith. Generally the mere raising of 
the lever by hand, or a few taps with a hammer if it 
be a pop valve, will free it and cause it to work all 
right again; but if this treatment has to be resorted to 
very often the valve should be taken down and over- 
hauled. In too many steam plants not enough import- 
ance is attached to the safety valve. The fact is, 
it is one of the most useful and important adjuncts oi 
a boiler, and if neglected serious results are sure to 
follow. 



80 ENGINEERING 

Feed Pumps. A good engineer will always take a 
pride in keeping his feed pump in good condition, and 
if he has two or more of them, which every steam 
plant of any consequence should have, he will have an 
opportunity to keep his pumps in good shape. The 
water pistons of most boiler feed pumps are fitted to 
receive rings of fibrous packing. The best packing for 
this purpose and one that will stand both hot and cold 
w^ater service is made of pure canvas cut in strips of 
the required width, J^, s/'^, Y^ in., etc., and laid 
together with a water proof cement having the edges 
for the wearing surface. This packing is called square 
canvas packing, and can be purchased in any size 
required for the pump. The size is easily ascertained 
by placing the water piston, minus the follower plate, 
centrally in the water cylinder and measuring the 
space between the piston and cylinder walls. This 
packing should not be allowed to run for too long a 
time before renewing, for the reason that pieces of it 
are liable to become loose and be forced along with 
the feed water on its way to the boiler and lodge 
under the check valve, holding it open and causing no 
end of trouble. If the feed pump has to handle hot 
water, or has to lift the water several feet by suction, 
the packing rings should be looked after at least once 
a month. 

Hard rubber valves are, all things considered, the 
best for a boiler feed pump, as they are not affected 
by hot water and do not hammer the seats like metallic 
composition valves do. Every boiler feed pump 
should be fitted with a good sight-feed lubricator for 
cylinder oil. The steam valve mechanism of a steam 
pump is very sensitive and delicate and requires good 
lubrication in order to do good work. In too many 



BOILER OPERATION 81 

cases feed pumps are fitted with an old style cylinder 
oil cup and there is generally more oil on the outside 
of the valve chest than there is inside, while the valve 
is bulldozed into working by frequent blows from a 
convenient club. 

The steam valves of all steam pumps are adjusted 
before they are sent out from the factory, and most of 
them are arranged so that the stroke may be 
shortened or lengthened as the engineer desires. It 
is best as a rule to allow a pump to make as long a 
stroke as it will without striking the heads, because 
then the parts are worn evenly. 

Sometimes an engineer is called upon to set the 
valves of a duplex pump which have become disar- 
ranged. In such a case he should proceed as follows: 
Place both pistons exactly at mid-stroke. This may 
be done in two ways. First, by dropping a plummet 
line alongside the levers connecting the rock shafts 
with the spools on the piston rods. Then bring the 
rods to the position where the centers of the spools 
will be in a vertical line with the centers of the rock 
shafts. 

The second method is to move the piston to 
the extreme end of the stroke until it comes in contact 
with the cylinder head. Then mark the rod at the 
face of the stuffing box gland. Next move the piston 
to the other end of the stroke and mark the rod at the 
opposite gland. Now make a mark on the rod exactly 
half way between the two outside marks and move the 
piston back until the middle mark is at the face of the 
gland and the piston will be at mid-stroke. Having 
placed both pistons at mid-strike, remove the valve 
chest covers and adjust the valves in their central posi- 
tion, viz., so that they cover the steam ports. Tht 



82 ENGINEERING 

valve rod being in position and connected to the 
rocker arm by means of the short link, the nut or nurs 
securing the valve to the rod should be so adjusted as 
to be equidistant from the lugs on the valve, say ^\ or 
^ of an inch according to the amount of lost motion 
desired, which latter factor governs the length of 
stroke in some makes of duplex pumps, while in 
others it is controlled by tappets on the valve rod 
outside of the valve chest. Care should be taken 
while making these adjustments that the valve be 
retained exactly in its central position. 

Having set the valv^es correctly, move one of the 
pistons far enough from mid-stroke to get a small 
opening of the steam port on the opposite side, then 
replace the valve chest covers and the pump will be 
ready to run. As these valves are generally made 
without any outside lap, a slight movement of one of 
the pistons in either direction from its central position 
will suffice to uncover one of the ports on the other 
cylinder sufficiently to start the pump. 

Sometimes duplex pumps "work lame," that is, 
one piston will make a quick full stroke while the 
other piston will move very slowly and just far enough 
to work the steam valve of the opposite side. In the 
majority of cases this irregular action is due to 
unequal friction in the packing of the rods, or the 
packing rings on one of the pistons may be worn out. 

If one side of a duplex pump becomes disabled from 
any cause, as breaking of piston rod in the water 
cylinder, for instance, which is liable to happen, the 
pump may still be operated in the following manner 
until duplicate parts to replace the broken ones have 
been secured. Loosen the nuts or tappets on the 
valve stem of the broken side and place them far 



BOILER OPERATION 83 

enough apart so that the steam valve will be moved 
through only a small portion of its stroke, thereby 
admitting only steam enough to move the empty 
steam piston and rod, and thus work the steam valve 
of the remaining side. The packing on the broken 
rod should be screwed up tight, so as to create as 
much friction as possible; there being no resistance in 
the water end. In this way the pump may be oper- 
ated for several days or weeks and thus prevent a shut 
down. 

Hydraulics for Engineers. Among the many difficult 
problems that are continually coming up for engineers 
to solve, there is none more perplexing than the cor- 
rect calculation of the quantity of water which will be 
discharged in a given time from pipes of various sizes 
and under the many different heads or pressures. 
Problems in hydraulics, as given by the majority of 
writers on engineering, are usually in elaborate alge- 
braical equations, which, to the ordinary working 
engineer, are very perplexing, at least the author has 
found them to be so in his experience. Therefore 
with a view of assisting his brother engineers in the 
solution of problems along this line which they may 
be called upon to solve, the author has spent consider- 
able time and labor in searching for and compiling a 
few rules and examples for hydraulic calculations in 
plain arithmetic which he hopes may be of benefit. 

First, to find velocity of flow in the pump, or in 
other words, piston speed. 

Rule. Multiply number of strokes per minute by 
length of stroke in feet, or fractions thereof. 

Second, the velocity of flow in the discharge pipe 
is in inverse ratio to the squares of the diameters of 
the pipe and the water cylinder of pumo. 



84 ENGINEERING 

Thus, a pump cylinder is 6 in. in diameter, and the 
piston speed is lOO ft. per minute; the discharge pipe 
being 3 in. in diameter. What is the velocity of^flow 
in the pipe? 

Example. 3^=4. In this case the velocity in the 
pipe is four times that in the pump, and 100 x 4 = 400 ft. 
per minute, velocity for water in the discharge pipe. 

Third, to find velocity in feet per minute necessary 
to discharge a given quantity of water in a given 
time. 

Rttle, Multiply the number of cubic feet to be dis- 
charged by 144 and divide by area of pipe in inches. 

Fourth, to find area of pipe when the volume and 
velocity of water to be discharged are known. 

Rule. Multiply volume in cubic feet by 144 and 
divide by the velocity in feet per minute. 

Fifth, one of the first requisites in making correct 
calculations of the quantity of water discharged from 
any sized pipe is to obtain the velocity of flow per 
second. There are several rules for doing this, among 
which the following appear to be the plainest and 
most simple: 

Rule I Multiply the square root of the head in 
inches by the constant 27.8. For instance, assume 
the head to be 100 ft. = 1200 in. The square root of 
1200 is 35 nearly, then 35 x 27.8 = 973 in. = 81 ft. per 
second velocity. 

Rule 2. Multiply the square root of the head in feet 
by the constant 8, as follows: The square of 100= 10 
and 10 X 8 = 80 ft. velocity per second. 

Rule J. Multiply twice the acceleration of gravity 
by the head in feet and extract the square root of 
product. The acceleration of gravity may be consid- 
ered the constant number 32, neglecting decimals. 



BOILER OPERATION 85 

32 X 2 X 100 = 6400. Square root of 6400 = 80 ft. per 
second. 

In many instances it is more convenient to use the 
pressure in pounds per square inch as shown by gauge 
instead of the height or head, and we can then apply 
Rule 4. 

Rule 4. Multiply the square root of the pressure in 
pounds per square inch by the constant number 12.16 
as follows: Pressure due to 100 ft. head -44 lbs., 
nearly. Square root of 44 = 6.6, which multiplied by 
12.16 = 80.2 ft. velocity per second. 

Having ascertained the velocity of flow, we may 
now proceed to calculate the weight of water in 
pounds per second discharged from any size of pipe, 
neglecting for the time being the loss in pressure 
caused by friction from elbows and bends in the pipe 
and also the peculiar shape assumed by a stream of 
water flowing through pipes or conduits when there ib 
no resistance except the pressure of the atmosphere 
and friction caused by long distance transmission. 

We will take for our calculation a four-inch pipe 
from which the water has a free flow under a head of 
100 ft., which gives a velocity of 80 ft. per second. 

Rule ^, Divide the velocity in feet per second by the 
constant 2.3, and multiply the quotient by the area of 
discharge pipe in square inches. 80 - 2.3 = 34.7. 
Now the area of a four-inch pipe is 12.57 sq. in., and 
34.7 X 12.57 = 436 lbs. discharged per second. 

In order to get the matter clearly before us, let us 
assume that we have a section of four-inch pipe just 
80 ft. in length and that it lies in a horizontal position 
and is filled solidly full of water. It will contain area, 
12.57 sq. in. X length, 960 in. = 12,067.2 cu. in. of water, 
and as one pound of water occupies a space of 



86 ENGINEERING 

27.7 cu. in., we therefore have 1,2067.2 ^ 2y.y ■= 436 lbs. 
of water, and at a velocity of 80 ft. per second our 
pipe will be emptied and refilled continuously each 
second. We have also Rule 6 to find the number of 
cubic feet discharged per minute when the velocity 
per minute is known. 

Ride 6. Multiply the area of pipe in square inches 
by the velocity in feet per minute and divide by the 
constant 144. 

Example. Area of 4 in. pipe = 12.57 sq. in. Velocity 
of flow = 80 ft. per second = 4,800 ft. per minute. Then 
i2^^x_4^^^j^ cu. ft. per minute -6.99 cu. ft. per 
second, which multiplied by 62.3 lbs. (weight of I cu. 
ft.) = 435.4 lbs. per second. 

As stated before, no allowance is made by the above 
rules for friction or other retarding influences, but for 
ordinary purposes in connection with a steam plant a 
deduction of 25 per cent, is probably sufficient. Of 
course if the water is being discharged into an elevated 
tank or against direct pressure of any kind, the resist- 
ance in pounds per square inch or the height in feet 
must be deducted from the impelling pressure or head. 
Let us assume, for instance, that our 4 in. pipe is dis- 
charging water into a tank at an elevation of 75 ft. 
above the level of the pump, and that to reach the 
tank requires 100 ft. of pipe with two 90° ells and one 
straight-way valve. We wish to discharge 500 gal. 
per minute into the tank ana will therefore require a 
velocity of about 13 ft. per second, which will necessi- 
tate a pressure of a little more than i lb. per square 
inch to be maintained at the pump over and above all 
resistance. Now the resistance to be overcome in this 
case will be: 



BOILER OPERATION 87 

Pressure per square inch due to 75 ft. head, 32.5 lbs. 
Friction loss due to length of pipe and velocity, 7.43 
Friction loss due to two go° ells, 2.16 

Friction loss due to straight way valve, .2 

Total, 42.29 lbs. 
Requiring a pressure of say 43 lbs. per square inch, 
or about the equivalent of lOO ft. head at the pump. 

Again, suppose that in place of the elevated tank 
we have 1,000 ft. of 8 in. horizontal pipe with a 4 in. 
delivery at the end farthest from the pump, and three 
branch pipes each 100 ft. long and 4 in. in diameter 
with one 90° ell and one straight-way valve, connected 
at intervals to the 8 in. main, and it is required to dis- 
charge in all 1,000 gals, per minute, or at the rate of 
250 gals, per minute for each 4 in. delivery. The 
friction loss for each 100 ft. in length of 8 in. pipe at 
a velocity of 13 ft. per second is .94 lbs., and for each 
100 ft. of 4 in. pipe it is 1.89 lbs. Likewise the 
friction loss for' each 90° ell is 1.08 lbs., and for a 
straight way valve .2 lbs., at the above velocity. The 
total resistance therefore to be overcome is as follows: 
For 1,000 ft. of 8 in. pipe, .94 lbs. x 10 = 9.4 lbs. 
For 300 ft. of 4 in. pipe, 1.89 lbs. x 3 = 5.67 " 
For four 90"^ ells, 1.08 lbs. x 4 = 4.32 " 

For four straight-way valves, .2 lbs. x 4= .8 '' 

Total, 20.19 Jbs. 
Consequently the pressure required at the pump wiU 
be about 22 lbs. per square inch, equal to a head of 
50 ft. 

Questions 

I. What should be the first care of an engineer on 
entering his boiler room when he goes on watch? 



88 ENGINEERING 

2. What is one of the duties of the fireman before 
coming- off watch? 

3. Name the various tools necessary for cleaning 
fires properly. 

4. Describe the operation of cleaning fires. 

5. What general rules should be observed in firing? 

6. How may the best results be obtained in firing 
bituminous coal? 

7. What will be the result if a sufficient supply of 
oxygen is not admitted to the furnace? 

8. What quantity of air (cubic feet or pounds 
weight) is required for the complete combustion of 
one pound of coal? 

g. Suppose there is a fusible plug in the boiler and 
it becomes covered with scale, what will be the result? 

10. How long may a boiler be run safely after wash- 
ing it out? 

11. What should be done with a boiler in order to 
prepare it for washing out? 

12. What effect does the too sudden cooling off or 
firing up of a boiler have upon the seams? 

13. What other bad result takes place within the 
boiler when it is emptied of water while hot? 

14. What should be done with tubes that have 
.become badly scaled? 

15. How fast should the feed water be supplied? 

16. What should be done in case the supply of feed 
water be cut off suddenly? 

17. What is the proper method of connecting a 
recently fired up boiler to the main header? 

18. What are some of the dangerous results of 
foaming? 

19. What can be done to prevent or at least to 
modify foaming in boilers? 



BOILER OPERATION 89 

20. Which are the most reliable pop valves or lever 
safety valves? 

21. What is the rule regulating the area of lever 
safety valves? 

22. What two factors must first be known before cor- 
rect calculations can be made as to the weight and posi- 
tion of the ball on a lever safety valve? 

23. How may the effective weight of the lever and 
that of the valve and stem be found? 

24. When the area in square inches of the valve, the 
weight of the valve and stem, the effective weight of 
the lever, the weight of the ball and its distance from 
the fulcrum are known, how is the pressure at which 
the valve will blow off ascertained? 

25. When the pressure at which the valve should 
blow off is known, together with the weights of all the 
parts, how may the distance the ball should be from 
the fulcrum be ascertained? 

26. When the pressure is known, together with the 
distance of the ball from the fulcrum, how is the 
weight of the ball found? 

27. What should be done with a safety valve in 
order to keep it in good working condition? 

28. Describe the process of setting the steam valves 
of a duplex pump. 

29. How may a duplex pump be operated in case 
one of the water pistons becomes disabled? 

30. How is the velocity of flow or piston speed per 
minute of a pump ascertained? 

31. The piston speed being known, how is the velo- 
city of flow in the discharge pipe found? 

32. When it is required to discharge a certain quantity 
of water from a given size of pipe in a given time, how 
may the velocity of flow in feet per minute be found? 



90 ENGINEERING 

33. When the volume of water to be discharged and 
the velocity of flow are known, how is the area of the 
pipe obtained? 

34. What is meant by "acceleration of gravity, " and 
what constant number represents it in connection with 
hydraulics? 

35. What per cent, of allowance is ordinarily made 
for friction in water pipes? 



CHAPTER IV 

COMBUSTION— WATER— STEAM 

Combustion — Composition of air — Carbon — The principal constit- 
uent of fuels — Hydrogen, its nature and heating value- 
Table, giving analysis of various coals — Process of combus- 
tion described — Quantity of air required — Furnace tempera- 
ture — How to utilize the heat in the escaping gases — Heat, 
what it is and how produced — Joule's researches — The heat 
unit — Specific heat — Sensible heat and latent heat — Experi- 
ments of Professor Black — Total heat of evaporation — Water, 
its composition, nature, etc. — Steam, its expansive nature, 
temperature, etc. — Saturated steam, etc. — Total heat of 
steam — Density of steam. 

Combustion. The subject of the combustion of fuels 
being one in which every engineer is vitally interested, 
it is proper that its leading features and principles be 
discussed. One of the main factors in the combustion 
of coal is the proper supply of air. Air is composed 
of two gases, oxygen and nitrogen, in the proportion, 
by volume, of 21 per cent, of oxygen and 79 per cent, 
of nitrogen, or by weight, 23 per cent, of oxygen and 
yy per cent, of nitrogen. 

The composition of pure dry air, as given by Kent 
in Steam Boiler Economy^ is as follows: 

By volume, 20.91 parts O. and 79.09 parts N. 

By weight, 23.15 parts O. and 76.85 parts N. 

Air is a mixture and not a chemical combination of 
these two elements. The principal constituent of coal 
and most other fuels, whether solid, liquid or gaseous, 
is carbon. Hydrogen is a light combustible gas and 
con^^bined either with carbon or with carbon and 

91 



ENGINEERING 



oxygen, in various proportions, is also a valuable con- 
stituent of fuels, notably of bituminous coal. The 
heating value of one pound of pure carbon is rated at 
14,500 heat units, while one pound of hydrogen gas 
contains 62,000 heat units. 

Analysis of coal shows that it contains moisture, 
fixed carbon, volatile matter, ash and sulphur in vari- 
ous proportions according to the quality of the coal. 
The following table deduced from a few of the many 
valuable tables of analysis of the coals of the United 
States, as given by Mr. Kent, wnll show the composi- 
tion of the principal bituminous coals in use in this 
country for steam purposes. Two samples are selected 
from each of the great coal producing states, with the 
exception of Illinois, from w^hich four were taken. 

Table 2 



State 


Kind of Coal 


Moist- 
ure 


Vola- 
tile 
Matter 


Fixed 
Carbon 


Ash 


Sul- 
phur 


Pennsylvania 


Youghiogheny 


1.03 


36.49 


59.05 


2.61 


0.81 


" 


Connellsville 


1.26 


30.10 


59.61 


8.23 


0.78 


West Virginia 


Quinimont 


0.76 


18.65 


79.26 


I. II 


0.23 


' ' 


Fire Creek 


o.6r 


22.34 


75.02 


1.47 


0.56 


E. Kentucky 


Peach Orchard 


4.60 


35-70 


53.28 


6.42 


1.08 


*' 


Pike County 


1.80 


26.80 


67.60 


3.80 


0.97 


Alabama 


Cahaba 


1.66 


33.28 


63.04 


2.02 


0.53 


'• 


Pratt Co.'s 


1-47 


32.29 


59.50 


6.73 


1.22 


Ohio 


Hocking Valley 


6.59 


35.77 


49.64 


8.00 


1.59 


** 


Muskingum " 


3.47 


37.88 


53.30 


5.35 


2.24 


Indiana 


Block 


8.50 


31.00 


57.50 


3.00 




< « 


' * 


2.50 


44.75 


51-25 


1.50 




W. Kentucky 


Nolin River 


4.70 


33.24 


54. Q4 


11.70 


2.54 


( i 


Ohio County 


3.70 


30.70 


45.00 


3.16 


1.24 


Illinois 


Big Muddy 


6.40 


30.60 


54.60 


8.30 


1.50 


< < 


Wilmington 


15.50 


32.80 


39-90 


11.80 




< ( 


" screenings 


14.00 


28.00 


34.20 


23.80 






Duquoin 


8.90 


23.50 


60.60 


7.00 





The process of combustion consists in the union of 
the carbon and hydrogen of the fuel with the oxygen 



COMBUSTION — WATER — STEAM 98 

of the air. Each atom of carbon combines with two 
atoms of oxygen, and the energetic vibration set up by 
their combination is heat. Bituminous coal contains a 
large percentage of volatile matter which is released 
and flashes into flame when the coal is thrown into the 
furnace, and unless air is supplied in large amounts at 
this stage of the combustion there will be an excess o) 
smoke and consequent loss of carbon. On the other 
hand there is a loss in admitting too much air because 
the surplus is heated to the temperature of the furnace 
without aiding the combustion and will carry off to 
the chimney just as many heat units as were required 
to raise it from the temperature at which it entered 
the furnace to that at which it enters the uptake. It 
will therefore be seen that a great advantage will be 
gained by first allowing the air that is needed above 
the fire to pass over or through heated bridge walls or 
side walls. Some kinds of coal need more air for 
their combustion than do others, and good judgment 
and close observation are needed on the part of the 
fireman to properly regulate the supply. 

Some boilers will make steam more economically by 
partly closing the ash-pit doors, while others require 
the same doors to be kept wide open. The quantity 
of air required for the combustion of one pound of 
coal is, by volume, about 150 cu. ft.; by weight, about 
12 lbs. 

The temperature of the furnace is usually about 
2500°, in some cases reaching as high as 3000°. The 
temperature of the escaping gases should not be much 
above nor below 400° F. for bituminous coal. The 
waste heat in the escaping gases can be utilized to 
great advantage by passing them through what are 
called economizers before they escape into the chim- 



94 ENGINEERING 

ney. These economizers consist of coils or stacks of 
cast iron pipe placed within the flue or breeching lead- 
ing from the boilers to the chimney and are enveloped 
in the hot gases, while the feed water is passed 
through the pipes on its way to the boilers, the result 
being that considerable heat is thus imparted to the 
feed water that would otherwise go to waste. 

In order to attain the highest economy in the burn- 
ing of coal in boiler furnaces two factors are indispen- 



^.w 




green's fuel economizer under construction. 

sable, viz., a constant high furnace temperature and 
quick combustion, and these factors can only be 
secured by supplying the fresh coal constantly just as 
fast as it is burned, and also by preventing as much as 
possible the admission of cold air to the furnace. 
This is why the automatic or mechanical stoker, if it 
be of the proper design, is more economical and 
causes less smoke than hand firing. The fireman 
when he puts in a fire is prone to shovel in a good 
supply all at once, and this has the tendency to 



COMBUSTION WATER — STEAM 95 

greatly reduce the temperature of the furnace, while 
at the same time it retards combustion. On the other 
hand the mechanical stoker supplies the coal continu- 
ously only as fast as it is required and no faster, and 
the furnace doors do not need to be opened at all, by 
which a large volume of cold air is prevented from 
entering the furnace and reducing the temperature. 
The author does not wish to be understood as recom- 
mending the adoption and use of mechanical stokers 
to replace hand firing, but he draws this contrast 
between the two methods of firing in order that it 
n\3.y be of some benefit to the thousands of honest 
toilers who earn a livelihood by shoveling coal into 
boiler furnaces. 

The problem of the economical use of coal and the 
abatement of the smoke nuisance, especially in our 
large cities, has of late years become so serious that it 
is to the interest of every engineer, and especially 
every fireman, to use the utmost diligence, care and 
good judgment in the use of coal, and to emulate as 
much as possible the methods of the mechanical 
stoker. 

Heat. All matter, whether solid, liquid or gaseous, 
consists of molecules or atoms, which are in a state of 
continual vibration, and the result of this vibration is 
heat. The intensity of the heat evolved depends upon 
the degree of agitation tp which the molecules are 
subject. 

Until as late as the beginning of the nineteenth 
century two rival theories in regard to the nature of 
heat had been advocated by scientists. The older of 
these theories was that heat was a material substance, 
a subtle elastic fluid termed caloric, and that this fluid 
penetrated matter something like water penetrates a 



96 ENGINEERING 

sponge. But this theory was shown to be false by the 
wonderful researches and experiments of Count Rum- 
ford at Munich, Bavaria, in 1798. 

By means of the friction between two heavy metallic 
bodies placed in a wooden trough filled with water, 
one of the pieces of metal being rotated by machinery 
driven by horses, Count Rumford succeeded in raising 
the temperature of the water in two and one-half 
hours from its original temperature of 60° to 212° F., 
the boiling point, thus demonstrating that heat is not 
a material substance, but that it is due to vibration or 
motion, an internal commotion among the molecules 
of matter. This theory, known as the Kinetic theory 
of heat, has since been generally accepted, although it 
was nearly fifty years after Rumford advocated it in a 
paper read before the Royal Society of Great Britain 
in 1798, before scientists generally became converted 
to this idea of the nature of heat and the science of 
Thermo Dynamics placed on a firm basis. 

During the period from 1840 to 1849 Dr. Joule made 
a series of experiments which not only confirmed the 
truth of Count Rumford's theory that heat was not a 
material substance but a form of energy which may be 
applied to or taken away from bodies, but Joule's 
experiments also established a method of estimating 
in mechanical units or foot pounds the amount of that 
energy. This latter was a most important discovery 
because by means of it the exact relation between heat 
and work can be accurately measured. 

The first law of thermo dynamics is this: Heat and 
mechanical energy or work are mutually convertible. 
That is, a certain amount of work will produce a 
certain amount of heat, and the heat thus produced is 
capable of producing by its disappearance a fixed 



COMBUSTION — WATER — STEAM 



97 



amount of mechanical energy if rightly applied. The 
mechanical energy in the form of heat which, through 
the medium of the steam engine, has revoluticL'zed 
the world, was first stored up by the sun's beat 
millions of years ago in the coal which in turn, b 





^^^3^t7U^^ \~J\ '^ 









f-2 

- r 

- 7 

H 



^ 



FIGURE 11 



combustion, is made to release it for purposes of 
mechanical work. 

The general principles of Dr. Joule's device for 
measuring the amount of work in heat are illustrated 
in Fig. II. It consisted of a small copper cylinder 



9o ENGINEERING 

containing a known quantity of water at a known 
temperature. Inside the cylinder and extending 
through the top was a vertical shaft to which were 
fixed paddles for stirring the water. Stationary vanes 
were also placed inside the cylinder. Motion was 
imparted to the shaft through the medium of a cord 
or small rope coiled around a drum near the top 'of the 
shaft and running over a grooved pulley or sheave. 
To the free end of the cord a known w^eight was 
attached. This weight was allowed to fall through a 
certain distance, and in falling it turned the shaft 
with its paddles, which in turn agitated the water, 
thus producing a certain amount of heat. To illus- 
trate, suppose the weight to be 77.8 lbs., and that by 
means of the crank at the top end of the shaft it has 
been raised to the zero mark at the top of the scale. 
(See Fig. 11.) One pound of water at 39.1° F. is 
poured into the copper cylinder, which is then closed 
and the weight released. At the moment the weight 
passes the 10 ft. mark on the scale, the thermometer 
attached to the cylinder will indicate that the temper- 
ature of the water has been raised one degree. Then 
multiplying the number of pounds in the weight by 
the distance in feet through which it fell will give the 
number of foot pounds of work done. Thus, 
77.8 lbs. X 10 ft. = 778 foot pounds. 

The heat unit or British thermal unit (B. T. U.) is 
the quantity of heat required to raise the temperature 
of one pound of water one degree, or from 39° to 
40° F., and the amount of mechanical work required 
to produce a unit of heat is 778 foot pounds. There- 
fore the mechanical equivalent of heat is the energy 
required to raise 778 lbs. one foot high, or 77.8 lbs. 
ID ft. high, or I lb. 778 feet high. Or again, suppose 



COMBUSTION WATER — STEAM 99 

a one-pound weight falls through a space of 778 ft. or 
a weight of 778 lbs. falls one foot, enough mechanical 
energy would thus be developed to raise a pound of 
water one degree in temperature, provided all the 
energy so developed could be utilized in churning or 
stirring the water, as in Joule's machine. Hence the 
mechanical equivalent of heat is 778 foot pounds. 

Specific Heat. The specific heat of any substance is 
the ratio of the quantity of heat required to raise a 
given weight of that substance one degree in temper- 
ature to the quantity of heat required to raise an equal 
weight of water one degree in temperature when the 
water is at its maximum density, 39.1° F. To illus- 
trate, take the specific heat of lead, for instance, which 
is .031, while the specific heat of water is i. That 
means that it would require 31 times as much heat to 
raise one pound of water one degree in temperature as 
it would to raise the temperature of a pound of lead 
one degree. 

The following table gives the specific heat of differ- 
ent substances in which engineers are most generally 

interested. 

TABLE 3. 

Water at 39.1° F i.ooo 

Ice at 32° F 504 

Steam at 212° F 480 

Mercury 033 

Cast iron 130 

Wrought iron 113 

Soft steel 116 

Copper 095 

Lead 031 

Coal 240 

Air 238 

Hydrogen 3.404 

Oxygen .^ 218 

Nitrogen 244 

Sensible Heat and Latent Heat. The plainest and 
most simple definition of these two terms is that given 



100 ENGINEERING 

by Sir VVm. Thomson. He says: "Heat giv^en to a 
body and warming it is sensible heat. Heat given to 
a body and not warming it is latent heat." Sensible 
heat in a substance is the heat that can be measured in 
degrees of a thermometer, while latent heat is the heat 
in any substance that is not shown by the ther- 
mometer. 

To illustrate this more fully a brief reftvence to 
some experiments made by Professor Black in 1762 
will no doubt make the matter plain. It will be 
remembered that at that early date comparatively 
little was known of the true nature of heat, hence Pro- 
fessor Black's investigations and discoveries along this 
line appear all the more wonderful. He procured 
equal weights of ice at 32"^ F. and water at the same 
temperature, that is, just at the freezing point, and 
placing them in separate glass vessels suspended the 
vessels in a room in which the uniform temperature 
was 47° F. He noticed that in one-half hour the 
water had increased 7° F. in temperature, but that 
twent}^ half hours elapsed before all of the ice was 
melted. Therefore he reasoned that twenty times 
more heat had entered the ice than had entered the 
water, because at the end of the twenty half hours 
when the ice was all melted the water in both vessels 
was of the same temperature. The water having 
absorbed 7° of heat during the first half hour must 
have continued to absorb heat at the same rate during 
the whole of the twenty half hours, although the ther- 
mometer did not indicate it. From this he calculated 
that 7° X 20 = 140° of heat had become latent or hidden 
in the water. 

In another experiment Professor Black placed a 
lump of melting ice which he estimated to be at a 



COMBUSTION — WATER — STEAM 101 

temperature of 33° F. on the surface, in a vessel con- 
taining the same weight of water at 176° F., and he 
observed that when the whole of the ice had been 
melted the temperature of the water was 33° F., thus 
proving that 143° of heat (176° — 33"") had been 
absorbed in melting the ice and was at that moment 
latent in the water By these two experiments Pro- 
fessor Black established the theory of the latent heat 
of water, and his estimate was very near the truth 
because the results obtained since that time by the 
greatest experimenters show that the latent heat of 
water is 142 heat units, or B. T. U. 

Black's experiment for ascertaining the latent heat 
in steam at atmospheric pressure was made in the 
following simple manner: He placed a flat, open tin 
dish on a hot plate over a fire and into the dish he put 
a small quantity of water at 50° F. In four minutes 
the water began to boil, and in twenty minutes more 
it had all evaporated. In the first four minutes the 
temperature had increased 212° — 50° = 162°, and the 
temperature remained at 212° throughout the twenty 
minutes that it required to evaporate all the water, 
despite the fact that the water had been receiving heat 
during this period at the same rate as during the first 
four minutes. He therefore reasoned that in the 
twenty minutes the water had absorbed five times as 
much heat as it had in the four minutes, or i6.?° x 
5 =- 8ia°, without any sensible rise in temperature. 
Therefore the 810° became latent in the steam. Owing 
to the crude nature of the experiment Professor 
Black's estimate of the number of degrees of latent 
heat in steam was incorrect, as it has been proven by 
many famous experimenters since then that the latent 
heat of steam at atmospheric pressure is 965.7 B. T. U. 



102 ENGINEERING 

It will thus be perceived that what is meant by the 
term latent heat is that quantity of heat which 
becomes hidden or latent when the state of a body is 
changed from a solid to a liquid, as in the case of 
melting ice, or from a liquid to a gaseous state, as 
with water evaporated into steam. But the heat so 
disappearing has not been lost, on the contrary it has, 
while becoming latent, been doing an immense amount 
of work, as can easily be ascertained by means of a 
few simple figures. It has been seen that a heat unit 
is the quantity of heat required to raise one pound of 
water one degree in temperature and also that the 
mechanical equivalent of heat, or, in other words, the 
mechanical energy stored in one heat unit is equal to 
778 foot pounds of work. 

A horse power equals 33,000 ft. lbs. of energy in 
one minute of time, and a heat unit = 778 -f- 33,000 = 
.0236, or about -^^ of a horse power. The work done 
by the heat which becomes latent in converting one 
pound of ice at 32° F. into water at the same temper- 
ature = 142 heat units x 778 ft. lbs. = 110,476 ft. 
lbs., which divided by 33,000 equals 3.34 horse 
power. Again, by the evaporation of one pound 
of water from 32° F. into steam at atmospheric 
pressure, 965.7 units of heat become latent in the 
steam and the work done = 965.7 x 778 = 751,314 ft. 
lbs. =22.7 horse power. It will thus be seen what 
tremendous energy lies stored in one pound of coal, 
which contains from 12,000 to 14,500 heat units, pro- 
vided all the heat could be utilized in an engine. 

Total Heat of Evaporation. In order to raise the tem- 
perature of one pound of water from the freezing 
point, 32° F., to the boiling point, 212° F., there must 
be added to the temperature of the water 212° — 32° = 



COMBUSTION — WATER STEAM lOS 

i8o°. This represents the sensible heat Then to 
make the water boil at atmospheric pressure, or, in 
other words, to evaporate it, there must still be added 
965.7 B. T. U., thus 180 + 965.7= 1,145.7, or in round 
numbers 1,146 heat units. This represents what is 
termed the total heat of evaporation at atmospheric 
pressure and is the sum of the sensible and latent heat 
in steam at that pressure. But if a thermometer were 
held in steam evaporating into the open air, as, for 
instance, in front of the spout of a tea-kettle, it would 
indicate but 212° F. 

When steam is generated at a higher pressure than 
212°, the sensible heat increases and the latent heat 
decreases slowly, while at the same time the total heat 
of evaporation slowly increases as the pressure 
increases, but not in the same ratio. As, for instance, 
the total heat in steam at atmospheric pressure is 
1,146 B. T. U. , while the total heat in steam at 100 lbs. 
gauge pressure is 1,185 B. T. U., and the sensible tem- 
perature of steam at atmospheric pressure is 212°, 
while at 100 lbs. gauge pressure the temperature is 338 
and the latent heat is 876 B. T. U. See table. 

Water. The elements that enter into the composi- 
tion of pure water are the two gases, hydrogen and 
oxygen, in the following proportions: 

By volume, hydrogen 2, oxygen I. 
By weight, " 11. i, " 88.9. 

Perfectly pure water is not attainable, neither is it 
desirable nor necessary to the welfare of the human 
race, because the presence of certain proportions of air 
and ammonia add greatly to its value as an agent for 
manufacturing purposes and for generating steam. 
The nearest approach to pure water is rain water, but 
even this contains 2.5 volumes of air to each 100 vol- 



104 ENGINEERING 

umes of water. Pure distilled water, such for instance 
as the return water from steam heating systems, is not 
desirable for use alone in a boiler as it will cause cor- 
rosion and pitting of the sheets, but if it is mixed with 
other water before going into the boiler its use is 
highly beneficial, as it will prevent to a certain degree 
the formation of scale and incrustation. Nearly all 
water used for the generation of steam in boilers con- 
tains more or less scale-forming matter, such as the 
carbonates of lime and magnesia, the sulphates of lime 
and magnesia, oxide of iron, silica and organic matte" 
which latter tends to cause foaming in boilers. 

The carbonates of lime and magnesia are the chief 
causes of incrustation. The sulphate of lime forms a 
hard crystalline scale which is extremely difficult to 
remove when once formed on the sheets and tubes of 
boilers. Of late years the intelligent application of 
chemistry to the analyzing of feed waters has been of 
great benefit to engineers and steam users, in that it 
has enabled them to properly treat the water with 
solvents either before it is pumped into the boiler, or 
by the introduction into the boiler of certain scale 
preventing compounds made especially for treating 
the particular kind of water used. Where it is neces- 
sary to treat water in this manner great care and 
watchfulness should be exercised by the engineer in 
the selection and use of a boiler compound. 

From ten to forty grains of mineral matter per 
gallon are held in solution by the w^aters of the differ- 
ent rivers, streams and lakes; well and mine water 
contain still more. 

Water contracts and becomes denser in cooling until 
it reaches a temperature of 39.1° F., its point of great- 
est density. Below this temperature it expands and 



COMBUSTION WATER STEAM 



105 



at 32° F. it becomes solid or freezes, and in the act of 
freezing it expands considerably, as every engineet 
who has had to deal with frozen water pipes can tes- 
tify. 

Water is 815 times heavier than atmospheric air. 
The weight of a cubic foot of water at 39. 1° is approx- 
imately 62.5 lbs., although authorities differ on this 
matter, some of them placing it at 62.379 lbs., and 
others at 62.425 lbs. per cubic foot. As its tempera- 
ture increases its weight per cubic foot decreases until 
at 212° F. one cubic foot weighs 59.76 lbs. 

The table which follows is compiled from various 
sources and gives the weight of a cubic foot of water 
at different temperatures. 

Table 4 



Temper- 


Weight per 


Temper- 


Weight per 


Temper- 


Weight per 


ature 


Cubic Foot 


ature 


Cubic Foot 


ature 


Cubic Foot 


32° F. 


62.42 lbs. 


132° F. 


61.52 lbs. 


230° F. 


59.37 lbs. 


42° 


62.42 


142° 


61.34 


240° 


59.10 


52° 


62.40 


152° 


61.14 


250° 


58.85 


62° 


62.36 


162° 


60.94 


260° 


58.52 


72° 


62.30 


172° 


60.73 


270° 


58.21 


82° 


62.21 


182° 


60.50 


300° 


57.26 


92° 


62.11 


iq2° 


60.27 


330° 


56.24 


102° 


62.00 


202° 


60.02 


360° 


55.16 


112° 


61.86 


212° 


59-76 


390° 


54-03 


122° 


61.70 


220° 


59.64 


420° 


52.86 



The boiling point of water varies according to the 
pressure to which it is subject. In the open air at sea 
level the boiling point is 212° F. When confined in a 
boiler under steam pressure the boiling point of water 
depends upon the pressure and temperature of the 
steam, as, for instance, at 100 lbs. gauge pressure the 
temperature of the steam is 338'' F., to which temper- 



106 ENGINEERING 

ature the water must be raised before its molecules 
will separate and be converted into steam. In the 
absence of any pressure, as in a perfect vacuum, water 
boils at 32° F. temperature. In a vacuum of 28 in., 
corresponding to an absolute pressure of .943 lbs., 
water will boil at 100°, and in a vacuum of 26 in., at 
which the absolute pressure is 2 lbs., the boiling point 
of water is 127"^ F. On the tops of high mountains in 
a rarefied atmosphere water will boil at a much lower 
temperature than at sea level, for instance at an 
altitude of 15,000 ft. above sea level water boils at 
184° F. 

Steam. Having discussed to some extent the phys- 
ical properties of water, it is now in order to devote 
some time to the study of the nature of steam, which 
is simply water in its gaseous form made so by the 
application of heat. 

As has been stated in another portion of this book, 
matter consists of molecules or atoms inconceivably 
small in size, yet each having an individuality, and in 
the case of solids or liquids, each having a mutual 
cohesion or attraction for the other, and all being in a 
state of continual vibration more or less violent 
according to the temperature of the body. 

The law of gravitation which holds the universe 
together, also exerts its wonderful influence on these 
atoms and causes them to hold together with more or 
less tenacity according to the nature of the substance. 
Thus it is much more difficult to chip off pieces of iron 
or granite than it is of wood. But in the case of water 
and other liquids the atoms, while they adhere to each 
other to a certain extent, still they are not so hard to 
separate, in fact, tney are to some extent repulsive to 
each other, and unless confined within certain bounds 



COMBUSTION — WATER STEAM 107 

the atoms will gradually scatter and spread out, and 
finally either be evaporated or sink out of sight in the 
earth's surface. Heat applied to any substance tends 
to accelerate the vibrations of the molecules, and if 
enough heat is applied it will reduce the hardest sub- 
stances to a liquid or gaseous state. 

The process of the generation of steam from water 
is simply an increase of the natural vibrations of the 
molecules of the water, caused by the application of 
heat until they lose all attraction for each other and 
become instead entirely repulsive, and unless confined 
will fly off into space. But being confined they con- 
tinually strike against the sides of the containing 
vessel, thus causing the pressure which steam or any 
other gas exerts when under confinement. 

Of course steam, like other gases, when under pres- 
sure is invisible, but the laws governing its action are 
well known. These laws, especially those relating to 
the expansion of steam, will be more fully discussed in 
the chapters on the Indicator. The temperature of 
steam in contact with the water from which it is 
generated, as for instance in the ordinary steam boiler, 
depends upon the pressure under which it is gener- 
ated. Thus at atmospheric pressure its temperature 
is 212° F. If the vessel is closed and the pressure 
increased the temperature of the steam and also that 
of the water rises. 

Saturated Steam, When steam is taken directly from 
the boiler to the engine without being superheated, it 
is termed saturated steam. This does not necessarily 
imply that it is wet and mixed with spray and 
moisture. 

Superheated Steam. When steam is conducted into 
or through a vessel or coils of pipe separate from the 



108 ENGINEERING 

boiler in which it was generated and is there heated to 
a higher temperature than that due to its pressure, it 
is said to be superheated. 

Dry Steam, When steam contains no moisture it is 
said to be dry. Dry steam may be either saturated or 
superheated. 

Wet Steam. When steam contains mist or spray 
intermingled it is termed wet steam, although it may 
have the same temperature as dry saturated steam of 
the same pressure. 

During the further consideration of steam in this 
book, saturated steam will be mainly under discussion 
for the reason that this is the normal condition of 
steam as used most generally in steam engines. 

Total Heat of Steam. The total heat in steam includes 
the heat required to raise the temperature of the water 
from 32° F. to the temperature of the steam plus the 
heat required to evaporate the water at that tempera- 
ture. • This latter heat becomes latent in the steam, 
and is therefore called the latent heat of steam. 

The work done by the heat acting within the mass of 
water and causing the molecules to rise to the surface 
is termed by scientists internal work, and the work 
done in compressing the steam already formed in the 
boiler or in pushing it against the superincumbent 
atmosphere, if the vessel be open, is termed external 
work. There are, therefore, in reality three elements 
to be taken into consideration in estimating the total 
heat of steam, but as the heat expended in doing 
external work is done within the mass itself it may, for 
practical purposes, be included in the general term 
latent heat of steam. 

De7isity of Steam. The expression density of steam 
means the actual weight in pounds or fractions of a 



COMBUSTION WATER STEAM 109 

pound avoirdupois of a given volume of steam, as one 
cubic foot. This is a very important point for young 
engineers especially to remember, so as not to get the 
two terms, pounds pressure and pounds weight, mixed, 
as some are prone to do. 

Volume of Steam. By this term is meant the volume 
as expressed by the number of cubic feet in one pound 
weight of steam. 

Relative Volume of Steam.. This expression has refer- 
ence to the number of volumes of steam produced 
from one volume of water. Thus the steam produced 
by the evaporation of one cubic foot of water from 
39° F. into steam at atmospheric pressure will occupy 
a space of 1646 cu. ft., but, as the steam is compressed 
and the pressure allowed to rise, the relative volume of 
the steam becomes smaller, as for instance at 100 lbs. 
gauge pressure the steam produced from one cubic 
foot of water will occupy but 237.6 cu. ft., and if the 
same steam was compressed to 1,000 lbs. absolute or 
985.3 lbs. gauge pressure it would then occupy only 
30 cu. ft. 

The condition of steam as regards its drvness may 
be approximately estimated by observing its appear- 
ance as it issues from a pet cock or other small open- 
ing into the atmosphere. Dry or nearly dry steam 
containing about i per cent, of muisture will be trans- 
parent close to the orifice through which it issues, and 
even if it is of a grayish white color it may be esti- 
mated to contain not over 2 per cent, of moisture. 

Steam in its relation to the engine should be consid- 
ered in the character of a vehicle for transferring the 
energy, created by the heat, from the boiler to the 
engine. For this reason all steam drums, headers and 
pipes should be thoroughly insulated in order to 



110 



ENGINEERING 



prevent, as much as possible, the loss of heat or energy 
by radiation. 

Table 5, showing the properties of saturated steam, 
is compiled mainly from Kent's Steam Boiler Economy. 
The decimals have not been carried out in the columns 
headed Relative Volume and Weight of i cu. ft. of 
steam, as their absence will affect the results very 
little. 



TABLE 5 
Properties of Saturated Steam 



>% 






Total 


Heat 






£ 





u 




U-i 


above 


32^ F. 


"c^ Cfl 


3 




. 


sfe 



a 


0) 

in 

en 

JO 

h4 




5 ^ 






'0 
> 


^3 




29.74 


.089 


32. 


0. 


1091.7 


I09I.7 


208,080 


3333.3 


.0003 


29.67 




122 


40. 


8. 


1094. 1 


1086. 1 


154,330 


2472.2 


.0004 


2g.56 




176 


50. 


18. 


1097.2 


1079.2 


107,630 


I724.I 


.0006 


29.40 




254 


60. 


28.01 


II00.2 


1072.2 


76,370 


1223.4 


.0008 


29.19 




359 


70. 


38.02 


1 103. 3 


1065.3 


54,660 


875.61 


.0011 


28.90 




502 


80. 


48.04 


1106.3 


1058.3 


39,690 


635.80 


.0016 


28.51 




692 


90. 


58.06 


110Q.4 


I05I.3 


20,290 


469.20 


.0021 


28.00 




943 


100. 


68.08 


1112.4 


1044.4 


21,830 


349.70 


.0028 


27.88 


I 




102. 1 


70.09 


1113.1 


1043.0 


20,623 


334.23 


.0030 


25.85 


2 




126.3 


94.44 


1120.5 


1026.0 


10,730 


173.23 


.0058 


23.83 


3 




141. 6 


109.9 


1125.1 


IOI5.3 


7,325 


118.00 


.0085 


21.78 


4 




I53.I 


121. 4 


1128.6 


1007.2 


5,588 


89.80 


.0111 


19.74 


5 




162.3 


130.7 


1131-4 


1000. 7 


4,F30 


72.50 


.0137 


17.70 


6 




170. 1 


138.6 


1133-8 


995.2 


3,816 


61.10 


.0163 


15.67 


7 




176.9 


145.4 


1135.9 


Q90. 5 


3,302 


53.00 


.0189 


13.63 


8 




182.9 


151. 5 


1137.7 


986.2 


2,912 


46.60 


.0214 


11.60 


9 




188.3 


156.9 


1139.4 


982.4 


2,607 


41.82 


.0239 


9.56 


10 




193.2 


161.9 


1140.9 


979.0 


2,361 


37.80 


.0264 


7.52 


II 




197.8 


166.5 


1142.3 


975.8 


2,159 


34.61 


.0289 


5.49 


12 




202.0 


170.7 


II43-5 


972.8 


1.990 


31.90 


.0314 


3.45 


13 




205.9 


174-7 


1 144. 7 


970.0 


1,846 


29.60 


.0338 


1. 41 


14 




209.6 


178.4 


1145.9 


967.4 


1,721 


27.50 


.0363 


0.00 


14 


7 


212.0 


180.9 


1146.6 


965.7 


1,646 


26.36 


.0379 



COMBUSTION WATER STEAM 



111 



Table 5 — Continued 





0) 




Total 


Heat 




0) 


B 





a a 


5d 




Above 


32«F. 


^ 


B 


dS 


(Si - 


pi— 1 


en'—' 


U^ 






rt tn 


a 




en rr 


1-S 


Q 


5 tn 

^ OS 


S en 

^ 'a 




'0 
> 

a; 

> 

'a; 


"S5 

3^ 


0^ 


0^ 


<; 






+2 <u 




:^ 


^^ 




0.3 


15 


213.3 


181. 9 


1146.9 


965.0 


1,614 


25.90 


.0387 


1-3 


16 


216.3 


185.3 


1147.9 


962.7 


1,519 


24.33 


.0411 


2.3 


17 


219.4 


188.4 


1148.9 


960.5 


1,434 


23.00 


.0435 


3.3 


18 


222.4 


191. 4 


1149.8 


958.3 


i,35Q 


21.80 


.0459 


4-3 


19 


225.2 


194.3 


1150.6 


956.3 


1,292 


20.70 


.0483 


5.3 


20 


227.9 


197.0 


1151.5 


954.4 


1,231 


19.72 


.0507 


6.3 


21 


230.5 


199.7 


1152.2 


952.6 


1,176 


18.84 


.0531 


7.3 


22 


233.0 


202.2 


1153.0 


950.8 


1,126 


18.03 


.0555 


8.3 


23 


235.4 


204.7 


1153.7 


Q49.I 


1,080 


17.30 


.0578 


9-3 


24 


237.8 


207.0 


1154.5 


947.4 


1,038 


16.62 


.0602 


10.3 


25 


240.0 


209.3 


1155.1 


945.8 


998 


16.00 


.0625 


II. 3 


26 


242.2 


211. 5 


1155.8 


944.3 


962 


15.42 


.0649 


12.3 


27 


2443 


213.7 


1156.4 


942.8 


929 


14.90 


.0672 


13.3 


28 


246.3 


215.7 


1157.1 


941.3 


898 


14.40 


.0696 


14.3 


29 


248.3 


2i;-8 


1157.7 


939.9 


869 


13.91 


.0719 


15.3 


30 


250.2 


219.7 


1158.3 


938.9 


841 


13.50 


.0742 


16.3 


31 


252.1 


221.6 


1158.8 


937.2 


816 


13.07 


.0765 


17.3 


32 


254.0 


223.5 


1159.4 


935.9 


792 


12.68 


.0788 


18.3 


33 


255.7 


225.3 


II 59.9 


934.6 


769 


12.32 


.0812 


19.3 


34 


257.5 


227.1 


1 160. 5 


933.4 


748 


12.00 


.0835 


20.3 


3=^ 


259.2 


228.8 


1161.0 


932.2 


728 


11.66 


.0858 


21.3 


36 


260.8 


230.5 


1161.5 


931.0 


709 


11.36 


.0880 


22.3 


37 


262.5 


232.1 


1162.0 


929.8 


691 


11.07 


.0903 


23-3 


38 


264.0 


233.8 


1 162. 5 


928.7 


674 


10.80 


.0926 


24.3 


39 


265.6 


235.4 


1162.9 


927.6 


658 


10.53 


.0949 


25.3 


40 


267.1 


236.9 


1163.4 


926.5 


642 


10.28 


.0972 


26.3 


41 


268.6 


238.^ 


1163.9 


925.4 


627 


10.05 


.0995 


27.3 


42 


270. 1 


240.0 


T164.3 


924.4 


613 


9.83 


.1018 


28.3 


43 


271.5 


241.4 


1164.7 


923.3 


600 


9.61 


.1040 


29.3 


44 


272.9 


242.9 


1165.2 


922.3 


587 


9.41 


.1063 


30.'3 


45 


274.3 


244.3 


1165.6 


921.3 


575 


9.21 


.1086 


31.3 


46 


275.7 


245.7 


1166.0 


Q20.4 


563 


9.02 


.1108 


32.3 


47 


277.0 


247.0 


1166.4 


919.4 


552 


8.84 


.1131 


33.3 


48 


278.3 


248.4 


1166.8 


918.5 


541 


8.67 


.1153 


34.3 


49 


279.6 


249.7 


1167.2 


917.5 


531 


8.50 


.1176 


35.3 


50 


280.9 


251.0 


1167.6 


916.6 


520 


8.34 


.1198 


36.3 


51 


282.1 


252.2 


1168.0 


915.7 


511 


8.19 


.1221 


37.3 


52 


283.3 


253.5 


1168.4 


914.9 


502 


8.04 


.1243 



112 



ENGINEERING 











Table 5 — Coiitimied 








0) 




Total Heat 




<u 


S 


"0 


^G 


ii 




above 


32»F. 


_^ 


E 


.S| 


(2^ 




Cfl 


[x* 






<x. m 


3 




,,j:2 


CD O" 


l^ 


^^ 




" in 


-^ 

— 13 


'0 
> 


r^ 


1^ 


^^ 




0) ^ 


CS .- 


03 -tj 


ci ^ 


OJ 


fe . 


^l 


§i^ 


-P. 




^-? 


■M C 


ii S 


-_2 


|5 


- D 


3 Cfi 


'0 ^ 


Q 


-*-" 


H^ ^ 


rt E 


OJ 


3 • 


■^^ 


axi 


^^ 




Zi rt 


?■ rt 




'^ 


U^ 




Oh-I 


< 




^ 0) 






C^ 


^hJ 


-^'0 
^ 


38.3 


53 


284.5 


254-7 


II68.7 


914.0 


492 


i 
7.90 


1266 


39- 


3 


54 


285.7 


256.0 


II69.1 


9I3-I 


484 


7-76 


1288 


40. 


3 


55 


286.9 


257.2 


1 169. 4 


912.3 


476 


7-63 


I3II 


41 


3 


56 


288.1 


258.3 


1169.8 


911.5 


468 


7.50 


1333 


42 


3 


57 


289.1 


259.5 


1 1 70. 1 


910.6 


460 


7.38 


1355 


43 


3 


58 


290.3 


260.7 


1170.5 


909.8 


453 


7.26 


1377 


44 


3 


59 


291.4 


261.8 


1170.8 


909.0 


446 


7.14 


1400 


45 


3 


60 


292.5 


262.9 


1171.2 


908.2 


439 


7.03 


1422 


46 


3 


61 


293.6 


264.0 


1171-5 


007.5 


432 


6.92 


1444 


47 


3 


62 


294.7 


265.1 


1171.8 


906.7 


425 


6.82 


1466 


48. 


3 


63 


295.7 


266.2 


1172.I 


905-9 


419 


6.72 


1488 


49- 


3 


64 


296.8 


267.2 


T172.4 


905.2 


413 


6.62 


I5II 


50. 


3 


65 


297.8 


268.3 


1172.8 


904-5 


407 


6.53 


1533 


51. 


3 


66 


298.8 


269.3 


1173-1 


903-7 


401 


6.43 


1555 


52 


3 


67 


299.8 


270.4 


II73-4 


903-0 


395 


6.34 


1577 


53 


3 


68 


300.8 


271.4 


1173-7 


902.3 


390 


6.25 


1599 


54 


3 


69 


301.8 


272.4 


1174.0 


901.6 


384 


6.17 


I62I 


55 


3 


70 


302.7 


273.4 


1174-3 


900.9 


379 


6.09 


1643 


56 


3 


71 


303.7 


274.4 


1174-6 


900.2 


374 


6.01 


1665 


57 


3 


72 


304.6 


275.3 


1174-8 


899.5 


369 


5.93 


1687 


58 


3 


73 


305.6 


276.3 


1175-I 


898.9 


365 


5.85 


1709 


59. 


3 


74 


306.5 


277.2 


1175-4 


898.2 


360 


5.78 


I73I 


60 


3 


75 


307-4 


278.2 


1175-7 


897.5 


356 


5.71 


1753 


61 


3 


76 


308.3 


279.1 


1176.0 


896.9 


351 


5.63 


1775 


62 


3 


77 


309.2 


280.0 


1176.2 


896.2 


347 


5.57 


1797 


63 


3 


78 


3 10. 1 


280.9 


1176.5 


895-6 


343 


5.50 


I8I9 


64 


3 


79 


310.9 


281.8 


1176.8 


895.0 


339 


5.43 


1840 


65 


3 


80 


311. 8 


282.7 


1177.0 


894-3 


334 


5.37 


1862 


66 


3 


81 


312.7 


283.6 


1177.3 


893-7 


331 


5.31 


1884 


67 


3 


82 


313.5 


284.5 


1177-6 


893.1 


327 


5.25 


1906 


68 


3 


83 


314.4 


285.3 


1177.8 


892.5 


323 


5.18 


1928 


69 


3 


84 


315.2 


286.2 


1178.1 


891.9 


320 


5.13 


1950 


70 


3 


85 


316.0 


287.0 


1178.3 


891.3 


316 


5.07 


I97I 


71 


3 


86 


316.8 


287.9 


1178.6 


890.7 


313 


5.02 


1993 


72 


•3 


87 


317.7 


288.7 


1178.8 


890.1 


309 


4.96 


2015 


73 


.3 


88 


318.5 


289.5 


1179.1 


889.5 


306 


4.91 


2036 


74 


.3 


89 


319.3 


290.4 


1179-3 


888.9 


303 


4.86 


2058 


75 


•3 


90 


320.0 


291.2 


1179.6 


888.4 


299 


4.81 


2080 



COMBUSTION WATER STEAM 



lis 



Table 5 — Contimced 





0) 




Total 


Heat 




1; 


E 





:3— ^ 


a a 

Cfil-H 


!ii 


above 


32«F. 


OS V) 


e 




<2i 




ID (U 




5 ^ 




0) -'-' 


> 




51 


3 -Si 

03 JD 


1^ 












s5 

03 




Ok4 


^^ 










^ 




76.3 


91 


320.8 


292.0 


1179.8 


887.8 


296 


4.76 


.2102 


77.3 


92 


321.6 


292.8 


1 1 80.0 


887.2 


293 


4.71 


.2123 


78.3 


93 


322.4 


293.6 


1180.3 


886.7 


290 


4.66 


.2145 


79-3 


94 


323.1 


294.4 


1 1 80. 5 


886.1 


287 


4.62 


.2166 


80.3 


95 


323.9 


295.1 


1 1 80 7 


885.6 


285 


4.57 


.2188 


81.3 


96 


324.6 


295.9 


1181.0 


885.0 


282 


4.53 


.2210 


82.3 


97 


325.4 


296.7 


1181.2 


884.5 


279 


4.48 


.2231 


83.3 


98 


326.1 


297.4 


1181.4 


884.0 


276 


4.44 


.2253 


84.3 


99 


326.8 


298.2 


1181.6 


883.4 


274 


4.40 


.2274 


85.3 


100 


327.6 


298.9 


1181.8 


882.9 


271 


4.36 


.2296 


86.3 


lOI 


328.3 


299.7 


1182.1 


882.4 


268 


4.32 


.2317 


87.3 


102 


329.0 


300.4 


1182.3 


881.9 


266 


4.28 


.2339 


88.S 


103 


329.7 


301. 1 


1182.5 


881.4 


264 


4.24 


.2360 


89.3 


104 


330.4 


301.9 


1182.7 


880.8 


261 


4.20 


.2382 


90-3 


105 


331. 1 


302.6 


1182.9 


880.3 


259 


4.16 


.2403 


91.3 


106 


331.8 


303.3 


1183.1 


879.8 


257 


4.12 


.2425 


92.3 


107 


332.5 


304.0 


1183.4 


879.3 


254 


4.09 


.2446 


93.3 


108 


333.2 


304.7 


1183.6 


878.8 


252 


4.05 


.2467 


94.3 


109 


333.9 


305.4 


1183.8 


878.3 


250 


4.02 


.2489 


95.3 


no 


334.5 


306.1 


1184.0 


877.9 


248 


3.Q8 


.2510 


96.3 


III 


335.2 


306.8 


1184.2 


877.4 


246 


3.95 


.2531 


97.3 


112 


335.9 


307.5 


1184.4 


876,9 


244 


3.92 


.2553 


98.3 


113 


33^.5 


308.2 


1184.6 


876.4 


242 


3.88 


.2574 


59.3 


114 


337.2 


308.8 


1184.8 


875.9 


240 


3.85 


.2596 


100.3 


115 


337.8 


309.^ 


1185.0 


875.5 


238 


3.82 


.2617 


101.3 


116 


338.5 


310.2 


1185.2 


875.0 


236 


3.79 


.2638 


102.3 


117 


339.1 


310.8 


1185.4 


874.5 


234 


3.76 


.2660 


103.3 


118 


339.7 


311. 5 


1185.6 


874.1 


232 


3.73 


.2681 


104.3 


119 


340.4 


312. 1 


1185.8 


873.6 


230 


3.70 


.2703 


105.3 


120 


341.0 


312.8 


1185.9 


873.2 


228 


3-67 


.2764 


106.3 


121 


341.6 


313.4 


1186.1 


872.7 


227 


3.64 


.2745 


107.3 


122 


342.2 


314.1 


1186.3 


872.3 


225 


3.62 


.2766 


108.3 


123 


342.9 


314.7 


1186.5 


871.8 


223 


3.59 


.2788 


109.3 


124 


343.5 


315.3 


1186.7 


871.4 


221 


3.56 


.2809 


1 10. 3 


125 


344.1 


316.0 


1186.9 


870.9 


220 


3.53 


.2830 


III. 3 


125 


344.7 


316.6 


1187.1 


870.5 


218 


3.51 


2851 


112. 3 


127 


345.3 


317.2 


1187.3 


870.0 


216 


3.48 


.2872 


113-3 


128 


345.9 


317.8 


1187.4 


86q.6 


215 


3.46 


.28^4 



114 



ENGINEERING 









Table ^~Co?itmued 








2^ . 




Total 


Heat 




QJ 


S 






03 . 


en . 


E oj 


Above 


32^ F. 


^.7 3 


s 

3 
> 


1^ 


cSj 


0, «- 


5 Cfi 


1 - 




<u 


<v 


OJ V- 


<A ^ 


0) — . 


^ 0) 







U 03 


4; a 
be . 


= =■ 


tl be 


^J 


^^§ 


> 


3? 


l-l ^ 


3 cn 


'0 ^ 


Q 


-C _y^ 


a;^^ 


^ X 


rt 


3 . 


^tn 


03^ 


mS^ 




n. rt 


S rt 


^ 




^3 


0^ 


OhJ 


<^ 










Csi 


. 


1143 


129 


346.5 


318.4 


II87.6 


869.2 


213 


3-43 


.2915 


115.3 


130 


347.1 


319-1 


II87.8 


868.7 


212 


3.41 


.2936 


116. 3 


131 


347.6 


319.7 


II88.O 


868.3 


210 


3.38 


.2957 


117.3 


132 


348.2 


320.3 


1188.2 


867.9 


209 


3.36 


.2978 


118.3 


133 


348.8 


320.8 


II88.3 


867.5 


207 


3.33 


.3000 


119. 3 


134 


349.4 


321.5 


II88.5 


867.0 


206 


3.31 


.3021 


120.3 


135 


350.0 


322. I 


II88.7 


866.6 


204 


3.29 


.3042 


121. 3 


136 


350.5 


322.6 


II88.9 


866.2 


203 


3.27 


.3063 


122.3 


137 


351. 1 


323.2 


IIS9.O 


865.8 


201 


3.24 


.3084 


123.3 


138 


351.8 


323.8 


II89.2 


865.4 


200 


3.22 


.3105 


124.3 


139 


352.2 


324.4 


II89.4 


865.0 


199 


3.20 


.3126 


125.3 


IdO 


352.8 


325-0 


I189.5 


864.6 


197 


3.18 


.3147 


126=3 


141 


353.3 


325.5 


I189.7 


864.2 


196 


3.16 


.3169 


127.3 


142 


353.9 


326.1 


I189.9 


863.8 


195 


3.14 


.3190 


128.3 


143 


354.4 


326.7 


II9O.O 


863.4 


193 


3. II 


.3211 


129.3 


144 


355.0 


327.2 


II9O.2 


863.0 


192 


3-09 


.3232 


130.3 


145 


355.5 


327.8 


II9O.4 


862.6 


191 


3.07 


.3253 


131.3 


146 


356.0 


328.4 


II9O.5 


862.2 


190 


3-05 


.3274 


133-3 


148 


357.1 


329.5 


II9O.9 


861.4 


187 


3.02 


.3316 


135.3 


150 


358.2 


330.6 


TI9I.2 


860.6 


185 


2.98 


.3358 


140.3 


155 


360.7 


333.2 


II92.O 


858.7 


179 


2.89 


•3463 


145-3 


160 


363.3 


335.9 


II92.7 


856.9 


174 


2.80 


.3567 


150.3 


165 


365.7 


338.4 


II93-5 


855.1 


169 


2.72 


.3671 


155.3 


170 


368.2 


340.9 


1194.2 


853.3 


164 


2.65 


.3775 


160.3 


175 


370.5 


343.4 


1194.9 


851.6 


160 


2.58 


.3870 


165.3 


180 


372.8 


345.8 


1195.7 


849-9 


156 


2.51 


.3983 


170.3 


185 


375.1 


348.1 


1196.3 


848.2 


152 


2.45 


.4087 


175.3 


190 


377.3 


350.4 


1197.0 


846.6 


148 


2.39 


.4191 


180.3 


195 


379-5 


352.7 


1197.7 


845.0 


144 


2.33 


.4296 


185.3 


200 


381.6 


354.9 


1198.3 


843-4 


141 


2.27 


.4400 


190.3 


205 


383.7 


357.1 


1 199.0 


841.9 


138 


2.22 


.4503 


195.3 


210 


385.7 


359-2 


1199.6 


840.4 


135 


2.17 


.4605 


200.3 


215 


387.7 


361.3 


1200.2 


838.9 


132 


2.12 


.4707 


205.3 


220 


389.7 


362.2 


1200.8 


838.6 


129 


2.06 


.4852 


245.3 


260 


404.4 


377-4 


1205.3 


827.9 


IIO 


1.76 


.5686 


28s. 3 


300 


417.4 


390.9 


1209.2 


818.3 


96 


1-53 


.6515 


485.3 


500 


467.4 


443.5 


1224.5 


781.0 


59 


-94 


1.062 


685.3 


700 


504.1 


482.4 


1235.7 


753.3 


42 


.68 


1-470 


985-3 


1000 


546.8 


528.3 


T248.7 


720.3 


30 


.48 


2.082 



combustion — water — steam 1 15 

Questions 

1. What is combustion? 

2. What is one of the main factors in combustion? 

3. Of what is air composed? 

4. In what proportion are these two gases combined? 

5. What is the principal constituent of coal and 
other fuels? 

6. What other valuable constituent is contained in 
bituminous coal? 

7. What is the usual temperature of a boiler furnace 
when in active operation? 

8. About what should be the temperature of the 
escaping gases? 

9. What two factors are indispensable in the eco- 
nomical use of coal? 

10. What is heat? 

11. What is the heat unit? 

12. What is the mechanical equivalent of heat? 

13. How many heat units are there in one pound of 
carbon? 

14. How many heat units are there in one pound of 
hydrogen gas? 

15. What is specific heat? 

16. What is sensible heat? 

17. What is latent heat? 

18. Is the latent heat imparted to a body lost? 

19. What is meant b}^ the total heat of evaporation? 

20. How much heat expressed in heat units is 
required to evaporate one pound of water from a tem- 
perature of 32° into steam at atmospheric pressure? 

21. Name the two elements composing pure water. 
22 In what proportion are these two gases combined 

in the formation of water? 



116 ENGINEERING 

23. Is perfectly pure water desirable for use in steam 
boilers? 

24. What causes scale to form in boilers? 

25. What proportion of mineral matter is usually 
found in water? 

26. What is steam? 

27. Of what does matter consist? 

28. How does the application of heat to any sub- 
stance affect its molecules? 

29. In what particular manner does heat affect the 
molecules of water? 

30. Is steam under pressure visible? 

31. What is saturated steam? 

32. What is dry steam? 

33. What is superheated steam? 

34. What is meant by the term total heat in steam? 

35. What is meant by the density of steam? 

36. What is meant by the volume of steam? 

37. What is the weight of a cubic foot of water at 
39.1° temperature? 

38. What is the weight of a cubic foot of water at a 
temperature of 212°? 

39. What is the boiling point of water in the open 
air at sea level? 

40. At what temperature will water boil in a perfect 
vacuum? 

41. What is meant by the relative volume of steam? 



CHAPTER V 

EVAPORATION TESTS 

Evaporation tests, object of — Preparing for a test — Suggestions as 
to apparatus needed — I'aking the temperature of the feed 
water — Precautions necessary to obtain accurate results- 
Duration of test — Feeding a boiler during a test — How to pro- 
ceed if the boiler is fed by an injector — Determining the per- 
centage of moisture in the steam — Moisture in the coal — 
Chimney draft — Draft gauge — Rules for determining the 
results of a test — "Equivalent evaporation," how to com- 
pute — Factors of evaporation — Boiler horse power. 

Evaporation Tests. The object of making evapora- 
tion tests of steam boilers is primarily to ascertain how 
many pounds of water the boilers are evaporating per 
pound of coal burned; but these tests can and should 
be made to determine several other important points 
with reference to the operation of the boilers, as for 
instance: i. The efficiency of the boiler and furnace 
as an apparatus for the consumption of fuel and the 
evaporation of water; whether this apparatus is per- 
forming its guaranteed duty in this respect, and how it 
compares with a known standard. 2. To aetermine 
the relative economy of different varieties of coal, also 
to determine the relative value of fuels other than 
coal, such as oil, gas, etc. 3. To ascertain whether or 
not the boilers as they are operated under ordinary 
every day conditions are being run as economically as 
they should be. 4. In case the boilers, owing to an 
increased demand for steam, fail to supply a sufficient 
quantity without forcing the tkes, whether or not addi- 
tional boilers are needed, or whether the trouble could 

117 



118 ENGINEERING 

be ovei'come by a change of conditions in operating 
them. 

As was stated in the chapter on boiler setting, every 
steam plant can and should be equipped with the 
necessary apparatus for making evaporation tests, and 
every engineer should take pride in making a good 
showing in the economical use of coal, and, be it said 
to their credit, the majority of engineers do this, 
although many of them are working under conditions 
that prevent them from doing all that they might 
desire along this line. Too many engineers are com- 
pelled to look after work entirely outside of and 
foreign to their vocation as engineers, often having to 
go to some distant part of the building to make repairs 
to some part of the machinery, leaving their boiler and 
engine to care for themselves for the time being, thus 
not only endangering the safety of property, but of 
life as well. But conditions are gradually changing 
for the better in this respect, and emplo};ers and own- 
ers of steam plants are coming more and more to rec- 
ognize the fact that the engineer is something more 
than a mere handy man about a factory, in fact, that 
he has a distinct and responsible vocation to be ful- 
filled, viz., the safe and economical operation of the 
plant where the power comes from. 

The author proposes to present in as brief a manner 
as possible a few simple suggestions and rules for the 
benefit of engineers who desire to make evaporation 
tests with a view of determining one or more of the 
points mentioned at the beginning of this chapter. 

Tests for the last three purposes named can be made 
by the regular engineering force of the plant, but in 
case a controversy should arise between the maker of 
the boiler and the purchaser regarding the first men- 



EVAPORATION TESTS 119 

tioned point, viz., the guaranteed efficiency of the 
boiler or the furnace, the services of experts in boiler 
testing may be resorted to. 

Preparing for a Test. All testing apparatus should be 
kept in such shape that it will not take three or four 
days to get it ready for making a test. On the con- 
trary, it can be and should be always kept in condition 
ready for use, so that the preparations for making a 
test will occupy but a short time. A small platform 
scale sufficiently large for weighing a wheel-barrow 
load of coal should also be provided in addition to the 
apparatus referred to in Chapter II. 

The capacity of each of the two tanks therein men- 
tioned, and which are illustrated in Fig. lO, can be 
determined in two ways, either by measuring the 
cubical contents oi each or by placing them one at a 
time on the scales, filling them with water to within a 
few inches of the top, and note the weight. Also make 
a permanent mark on the inside at the water level. 
The water should then be permitted to run out until 
within an inch or so of the outlet pipe near the bottom, 
where another plain mark should be made, after which 
the empty tank should be again weighed, then by sub- 
tracting the last weight from the first the exact number 
of pounds of water that the tank will contain between 
the top and bottom marks can be determined and a 
note made of it. 

It is much more convenient to have each tank con- 
tain the same quantity of water, although not abso- 
lutely necessary. The tanks should also be numbered 
I and 2 respectively in order to prevent confusion in 
keeping a record of the number of tanks full of water 
used during the test. Care should be exercised to 
have the water with which the tanks are filled while on 



120 ENGINEERING 

the scale, at or near the same temperature as that at 
which it is to be fed into the boiler during the test. 
Otherwise there is liability of error owing to the varia- 
tion in the weight of water at different temperatures. 
In order to guard against this, the capacity in cubic 
feet of each tank between the top and bottom marks 
should be ascertained by measuring the distance 
between the marks, also the diameter, or, if the tanks 
be square, the length of one side, after which the 
cubical contents can be easily figured and noted down. 
By knowing the capacity in cubic feet of each tank all 
possibility of error in the weight of feed water will be 
eliminated. 

The scales for weighing the coal can be fitted with a 
temporary wooden platform large enough to accom- 
modate a wheel-barrow, and after it has been balanced 
with the empty barrow on it, the record of weight of 
coal burned during the test can be easily kept. 

The same barrow should be used throughout the 
test, and to save complications in estimating the 
weight, the same number of pounds of coal should be 
filled in the barrow each load. The coal passer will 
learn in a short time to fill the barrow to within a few 
pounds of the same weight each load by counting the 
shovelsful and the difference can easily be adjusted by 
having a small box of coal near the scale from which 
to take a few lumps to balance the load, or if there is 
too much coal in the barrow some of it can be thrown 
into the box. 

At least two separate tally sheets should be provided, 
marked respectively coal and water, and the one for 
coal placed near the scale, and care should be taken 
that each load is tallied as soon as it is weighed. The 
tally sheet for water should be near the measuring 



EVAPORATION TESTS IJl 

tanks and as soon as a tank is emptied it should be 
tallied. The temperature of the feed water should be 
taken at least every thirty minutes, or oftener if pos- 
sible, from a thermometer placed in the feed pipe near 
the check valve, as described in Chapter 11. The 
readings should be noted and, at the expiration of the 
test, the average taken. 

If the object of the test is to ascertain the efficiency 
of the boiler and furnace it is absolutely necessary that 
the boiler and all its appurtenances be put in good 
condition, by cleaning the heating surface both inside 
the boiler and outside, scraping and blowing the soot 
out of the tubes if it be a return tubular boiler, and 
blowing the soot and ashes from between the tubes if 
it is a water tube boiler. All dust, soot and ashes 
should be removed from the outside of the shell and 
also from the combustion chamber and smoke connec- 
tions. The grate bars and sides of the furnace should 
be cleared of all clinker, and all air leaks made as 
close as possible. The boiler and all its water connec- 
tions should be free from leaks, especially the blow-off 
valve or cock. If any doubt exists as to the latter it 
should be plugged or a blind flange put on it. It is 
very essential that there should be no way for the 
water to leak out of the boiler, neither should any 
water be allowed to get into the boiler during the test 
except that which is measured by passing through the 
tanks. 

The engineer making the test should know the num- 
ber of square feet of grate surface and also the 
area of the heating surface in square feet. Rules 
for computing the latter are given in Chapter II. 
If the boiler is a water tube boiler the outside diameter 
of the tubes must be used in estimating the heating 



122 ENGINEERING 

surface. A correct knowledge of the above points is 
essential in making a test for determining any one of 
the four objects mentioned at the commencement of 
this chapter, but especially is it needed in conducting 
a test of the efficiency of the boiler and furnace. 

In making an efficiency test it is essential that the 
boiler should be run at its fullest capacity from the 
beginning to the end of the test. Therefore arrange- 
ments should be made to dispose of the steam as fast 
as it is generated. If the boiler is in a battery con- 
nected with a common header, its mates can be fired 
lighter during the test, but if there is but the one 
boiler in use a waste steam pipe should be temporarily 
connected through which the surplus steam, if there is 
any, can be discharged into the open air through a 
valve regulated as required. Before starting the test 
the boiler should be thoroughly heated by having 
been run several hours at the ordinary rate. The fire 
should then be cleaned and put in good condition to 
receive fresh coal. 

At the time of beginning the test the water level 
should be at or near the height ordinarily carried and 
its position marked by tying a cord around one of the 
guard rods of the gauge glass, and, to prevent all pos- , 
sibility of e^-ror, the height of the water in the glass 
should be measured and a note made of it. Note also 
the time that the first lot of weighed coal is fed to 
the furnace and record it as the starting time. The 
steam pressure should be noted at the beginning of 
the test and at regular intervals during the progress of 
the test in order that the average pressure may be 
obtained. 

At the close of the test all of the above conditions 
should be as nearly as possible the same as at the 



EVAPORATION TESTS 123 

beginning; the quantity and condition of the fire 
should be the same, also the steam pressure and water 
level. This can be accomplished only by careful work 
towards the close of the test. 

During the progress of the test care should be exer- 
cised to prevent any waste of coal, especially in clean- 
ing the fire. The ash made during the test must not 
be wet down until after it is weighed, as in all calcula- 
tions for combustible and non-combustible matter in 
the coal the ash should be dry. 

The duration of the test should be at least ten hours 
if it is possible to continue it for that length of time. 
The feed pump should be kept running at such speed 
as will supply the water to the boiler as fast as it is 
evaporated, and no faster. If at the close of the test 
a portion of water is left in the last tank tallied it can 
be measured and deducted from the total. And if any 
weighed coal is left on the floor it should be weighed 
back and deducted from the total weight. If the 
boiler is fed by an injector instead of a pump during 
the test, the injector should receive steam directly 
from the boiler under test through a well protected 
pipe. Also, the temperature of the feed water should 
be taken from the measuring tanks, or at least from 
the suction side of the injector, for the reason that the 
water in passing through the injector receives a large 
quantity of heat imparted to it by live steam directly 
from the boiler. Therefore the temperature of the 
water after it leaves the injector would not be a ^rue 
factor for figuring the evaporation. 

Detennination of the Percentage of Moisture in the 
Steam. This is an important point in estimating the 
results of an evaporation test for the reason that each 
pound weight of moisture in the steam as it leaves the 



124 ENGINEERING 

boiler represents a pound of water that has not been 
evaporated into steam, and should therefore be 
deducted from the total weight of water fed into the 
boiler during the test. 

The steam should be tested for moisture by taking 
samples of it from the steam pipe or header as neat 
the boiler as possible in order to guard against addi- 
tional moisture caused by condensation. For making 
expert boiler tests for scientific and other purposes, an 
instrument called a calorimeter is used for ascertaining 
the quantity of moisture in the steam. But most 
engineers are not so fortunate as to possess one of 
these instruments, nor even to induce their employers 
to purchase one, therefore space will not be taken up 
in describing it here. A method of testing the 
quality of the steam by noting the appearance of a 
small jet blowing into the atmosphere is mentioned 
near the close of Chapter IV, which in the absence of 
a calorimeter would answer very well for ordinary 
purposes. 

Moisture in the Coal. This can generally be obtained 
from the reports of the geologist of the state in which 
the coal is mined or from the dealer, although the 
former is the most reliable. The percentage of mois- 
ture must be deducted from the total weight of coal in 
figuring the weight of combustible. 

Measuring the Chimney Draft, A good draft is indis- 
pensable for obtaining economical results in an evap- 
oration test. The draft can be easily regulated by a 
damper to suit the conditions. Chimney draft is ordi- 
narily measured by a draft gauge connected with the 
smoke flue near the chimne}^ The usual form of draft 
gauge is a glass tube bent in the shape of the letter U. 
(See Fig. 12.) One leg is connected to the flue by a 



EVAPORATION TESTS 



125 




small rubber hose, while the other is open to the 
atmosphere. The tube is partly filled with water, 
which will, when there is no draft, stand at the same 
height in both legs. When connected to the chimney 
or flue the suction will cause the 
water in the leg to which the 
hose is attached to rise, while 
the level of the water in the 
other leg will be equally de- 
pressed, and the extent of the 
variation in fractions of an inch 
is the measure of the draft. Thus 
the draft is referred to as being 
.5, .7 or .75 inches. The draft 
should not be less than .5 inches 
in any case to insure good results. 

Having thus successfully con- 
ducted the test to its close, and 
being armed with all the data 
heretofore noted, the engineer 
is now ready to compute the 
results. 

If the test is made for the pur- 
pose of determining the effi- 
ciency of the boiler and setting 
as a whole, including grate, 
chimney draft, etc., then the 
result must be based upon the 
number of pounds of water evap- 
orated per pound of coal. This latter phrase includes 
not only the purely combustible matter in the coal, 
but the non-combustible aiso, as ash, moisture, etc. 
Some varieties of western coal contain as high as 12 to 
14 per cent, of moisture, and the ability of the furnace 




FIGURE 12. 



126 ENGINEERING 

to extract heat from the mass is to be tested, as well 
as the ability of the boiler to absorb and transmit that 
heat to the water. Therefore the efficiency of the 
boiler and furnace = 

Heat absorbed per pound of coal. 
Heating value of one pound of coal. 

If the test is to determine the efficiency of the boiler 
itself as an absorber of heat, then the combustible 
alone must be considered in working out the final 
result. Thus, 

Efficiency of boiler = 

Heat absorbed per pound of combustible. 
Heating value of one pound of combustible. 

When making a series of tests for the purpose of 
comparing the economical value of different varieties 
of coal the conditions should be as nearly uniform as 
possible; that is, let the tests be made under ordinary 
working conditions and with the same boiler or boil- 
ers, and if possible with the same fireman. 

The following is a record of one of many evapora- 
tion tests made by the author, and is introduced here 
for the purpose of illustrating methods of computing 
the results to be obtained from the various data. The 
rather large quantity of coal burned per square foot of 
grate surface per hour (25 lbs.) is owing to the fact 
that the boiler was run to its full capacity, the coal 
burning clean and forming no clinker. The chimney 
draft also was exceptionally good, giving a large unit 
of evaporation per square foot of heating surface per 
hour. The low temperature of the escaping gases is 
due to the fact that they were returned over the top of 
the boiler before passing to the chimney- 



EVAPORATION TESTS 127 

Date of test 

Duration of test, 12 hours. 
Boiler, return tubular, 72 in. diameter, 18 ft. long, 62-4^ in. tubes. 
Kind of coal, Pocahontas; average steam pressure. . 85 lbs. 

Weight of coal consumed 11, 100 * ' 

Weight of water apparently evaporated 107,187 ** 

Weight of dry ash returned 8.1 per cent.= goo ** 

Moisture in the coal 2.0 '* = 222 " 

Moisture in the steam i.o " = 1,071 ** 

Dry coal corrected for moisture 10,878 ** 

Weight of combustible 9,978 ** 

Water corrected for moisture in the steam 106,116 ** 

Water evaporated into dry steam, from and at 212°. .117,788 ** 
Water evaporated per lb. of coal, actual conditions. . 9.65 *' 

Water evaporated per lb. of coal, from and at 212°. . 10.61 " 

Water evaporated per lb. of combustible, from and 

at 212° II. 81 ** 

Water evaporated per lb. of dry coal, from and at 212° 10.82 ** 

Water evaporated per hr. per sq. ft. of heating surface 6.22 ** 

Coal burned per sq. ft. of grate surface per hour .... 25 ** 

Horse power developed by boiler during test 284.5 

Temperature of feed water, average 141" 

Temperature of chimney gases, average 400° 

Square feet of grate surface 36 

Square feet of heating surface 1576 

Ratio of grate surface to heating surface 43.7 

The results obtained will be taken up in their regu- 
lar order beginning with, first, water evaporated into 
dry steam from and at 212°. As it may be of benefit 
to some, a short definition of the meaning of the above 
expression is here given. 

The term "equivalent evaporation," or the evapora- 
tion from and at 212°, assumes that the feed water 
enters the boiler at a temperature of 212° and is evap- 
orated into steam at 212° temperature and at atmos- 
pheric pressure. As for instance, if the top man hole 
plate were left out or some other large opening in the 
steam space allowed the steam to escape into the 
atmosphere as fast as it was generated. Owing to 
the variation in the temperatures of the feed water 
used in different tests, and also the variation in the 
steam pressure, it is absolutely necessary that the 



128 ENGINEERING 

results of all tests be brought by computation to 
the common basis of 212° in order to obtain a just 
comparison. 

The process by which this is done is as follows: 
Referring to the record of the test it is seen that the 
steam pressure average was 85 lbs. gauge pressure, or 
100 lbs. absolute, and that the temperature of the feed 
water was 141°. Referring again to Table No. 5, phys- 
ical properties of steam, it will be seen that in a pound 
of steam at 100 lbs. absolute pressure there are 1,181.8 
heat units, and in a pound of water at 141° temperature 
there are 109.9 heat units. It therefore tookii8i.8 — 
109.9 = 1071.9 heat units to convert one pound of feed 
water at 141° into steam at 85 lbs. pressure. To con- 
vert a pound of water at 212° into steam at 
atmospheric pressure, and 212° temperature requires 
965.7 heat units, and the 1,071.9 heat units w^ould evap- 
orate 1,071.9 -^ 965.7 =1.11 lbs. water from and at 212°. 
The I. II is the factor of evaporation for 85 lbs. gauge 
pressure and 141° temperature of feed water, and by 
multiplying "water corrected for moisture in the 
steam'' (see record of test), 106,116 lbs., by i.ii, the 
weight of water which could have been evaporated into 
steam from and at 212°, is obtained, which is 117,788 
lbs. The factor of evaporation is based upon the 
steam pressure and the temperature of the feed water 
in any test and the formula for ascertaining it is as 

TT U 

follows: Factor = —^ , in which H = total heat in 

965.7' 

the steam, and h = total heat in the feed water. It 
is used in shortening the process of finding the evap- 
oration from and at 212°, and Table No. 6 gives the 
factor of evaporation for various pressures and tem- 
peratures. 



EVAPORATION TESTS 



129 



Table 6 
Factors of Evaporation 







CO 

|3 


CO 




en 




si 


i 

ai 

S M 


CO 


-2 ^ 


oi 


^ 


^ 

2^ 


^ 






0) 


OS . 
4> 


^1 


^H 


£ 


£ 


P-. 


£ 


Oh 


£ 


£ 


ii 


£ 


212° 


1.027 


1.030 


1.032 


1.035 


1.037 


1.039 


1. 041 


1.043 


1.047 


200° 


1.039 


1.042 


1.045 


1.047 


1.050 


1.052 


1.054 


1.056 


1.059 


191° 


1.049 


1.052 


1.054 


1.057 


1.059 


1. 061 


1.063 


1.065 


1.069 


182° 


1.058 


1. 061 


1.064 


1.066 


1.069 


1. 071 


1.073 


1.075 


1.078 


173° 


1.067 


1.070 


1.073 


1.076 


1.078 


1.080 


1.082 


1.084 


1.087 


164° 


1.077 


1.080 


1.083 


1.085 


1.087 


1.090 


1. 091 


1.093 


1.097 


152° 


1.089 


1.092 


i.ogs 


1.098 


1. 100 


1. 102 


1. 104 


1. 106 


1. 109 


143° 


1.099 


1. 102 


1. 105 


1. 107 


I. 109 


I.III 


1. 113 


1. 115 


1. 119 


134° 


1. 108 


I.III 


1. 114 


1. 116 


I. 119 


1. 121 


1. 123 


1. 125 


1. 128 


125° 


1. 118 


1. 121 


1. 123 


1. 126 


1. 128 


1. 130 


1. 132 


1. 134 


1. 137 


113° 


1. 130 


1. 133 


1. 136 


1. 138 


1. 140 


1. 143 


1. 145 


1. 146 


1. 150 


104° 


1. 138 


1. 142 


1. 145 


1. 148 


1. 150 


1. 152 


I. 154 


1. 156 


1. 159 


95° 


1.149 


1. 152 


1. 154 


1. 157 


I. 159 


1. 161 


I. 163 


1. 165 


1. 169 


86° 


1.158 


1. 161 


1. 164 


1. 166 


1. 169 


1. 171 


1. 173 


1. 174 


1. 178 


77° 


1. 167 


1. 170 


1. 173 


1. 176 


1. 178 


1. 180 


1. 182 


1. 1 84 


1.187 


65° 


1. 180 


1. 183 


1.186 


1. 188 


I. 190 


1. 192 


I. 194 


1. 196 


1.200 


56° 


1. 189 


1. 192 


1. 195 


1. 197 


1.200 


1.202 


1.204 


1.206 


1.209 


47° 


1. 199 


I. 201 


1.204 


1.207 


1.209 


I. 211 


1. 213 


1. 215 


1. 218 


38° 


1.208 


1. 211 


1. 214 


1. 216 


1. 218 


1.220 


1.222 


1.224 


1.228 



Second, water evaporated per pound of coal actual 
conditions = water apparently evaporated divided by 
coal consumed = 9.65 lbs. No accurate estimate 
regarding the quality of the coal or the efficiency of 
the boiler can be made from this figure (9.65 lbs.). It 
can be used, however, in estimating the cost of fuel for 
generating the steam; as, for instance, if the boiler is 
supplying steam to an engine that uses 30 lbs. of steam 
per horse power per hour, it will require 30 -^ 9.65 = 3.1 
lbs. of coal per horse power per hour; the "actual 
conditions" under which the boiler is being operated 
being the pressure of steam required by the engine 
and the temperature of the feed water. 



130 ENGINEERING 

Third, water evaporated per pound of coal from and 
at 212° = water evaporated into dry steam from and at 
212° divided by coal consumed = io.6i lbs. This fig- 
ure is the proper one to use in comparing the relative 
economic values of different varieties of coal tested 
with the same boiler or boilers. 

Fourth, water evaporated per pound of combustible 
from and at 212° = water evaporated into dry steam 
from and at 212° divided by weight of combustible 
= 1 1. 81 lbs. This result is the one to be used for 
ascertaining the efficiency of the boiler, and the per- 
centage of efficiency is found by dividing the heat 
absorbed by the boiler per pound of combustible by 
the heat value of one pound of combustible. The 
average heat value of bituminous and semi-bituminous 
coals is not far from 15,000 heat units per pound of 
combustible. In the evaporation of 11. 81 pounds of 
water from and at 212° the heat absorbed was 11. 81 x 
965.7 = 11,404.9 heat units. The efficiency of :re boiler 
therefore was 1M04|^= 76 per cent. 

In like manner to ascertain the efficiency of the 
boiler and furnace as a whole, the water evaporated 
from and at 212° per pound of coal is taken. Thus, 
10.61x965.7=10,246 heat units absorbed from each 
pound of coal Now assuming that there were 13,500 
heat units in each pound of the coal used in the test, 
the per cent of efficiency of boiler and furnace was 

10,246X100 _ ^^ p, 
13,500 ~ /5-9- 

Fifth, water evaporated per pound of dry coal from 

and at 212°= water evaporated into dry steam from 

and at 212° divided by coal corrected for moisture. 

Thus, 117,788- 10,878= 10.82 lbs. This result is useful 

for calculating the results of tests of the same grade 



EVAPORATION TESTS 131 

of coal, but differing in the degree of moisture in 
each. 

Sixth. Boiler horse power. The latest decision of 
the American Society of Mechanical Engineers (than 
whom there is no better authority) regarding the horse 
power of a boiler is as follows: "The unit of commer- 
cial horse power developed by a boiler shall be taken 
as 34^ units of evaporation per hour. That is, 34^^ 
lbs. of water evaporated per hour from a feed temper- 
ature of 212° into steam of the same temperature. 
This standard is equivalent to 33,317 B. T. U. per hour. 
It is also practically equivalent to an evaporation of 
30 lbs. of water from a feed water temperature of 100° 
F. into steam of 70 lbs. gauge pressure.*' 

According to this rule the horse power developed 
by the boiler during the test under consideration = watei 
evaporated into dry steam from and at 212°, 117,788 
lbs -4- 12 hrs. -f. 34. 5 = 284.5 horse power. 

Questions 

1. What is the primary object of an evaporation 
test? 

2. Name four other important points which can be 
determined by evaporation tests. 

3. In making a test of the efificiency of the boiler 
and furnace, what precautions should be observed? 

4. How is the heating surface of water tube boilers 
estimated? 

5. What length of time should a test be conducted? 

6. In case the boiler is fed by an injector, what pre- 
cautions are necessary? 

7. If the steam contains any moisture, what should 
be done? 

8. How is the weight of combustible determined? 



132 ENGINEERING 

9. What IS a calorimeter, and for what purpose is it 
used? 

10. By what other method may the moisture in the 
steam be estimated approximately? 

11. What should be done with the percentage of 
moisture in the coal? 

12. How is the chimney draft measured? 

13. Describe a draft gauge. 

14. Give the formula for ascertaining the efficiency 
of the boiler and setting. 

15. If the test is to determine the efficiency of the 
ooiler alone, what factors are used? 

16. If a series of tests is made for comparing differ- 
ent varieties of coal, what should be done? 

17. What is meant by equivalent evaporation? 

18. Why should the results of all tests be computed 
from and at 212°? 

ig. What is a factor of evaporation? 

20. How is it determined? 

21. What is a boiler horse power? 

22. How many heat units per hour is this equiv- 
alent to? 



CHAPTER VI 

VALVES AND VALVE SETTING 

Valves and valve setting — Importance of correct adjustment — The 
D slide valve — Single valve engines— Four valve engines — 
Various positions of the slide valve during one revolutian — 
Relative positions of the crank pin and eccentric during the 
stroke — Valve diagrams — Placing the engine on the center — 
Adjusting the length of eccentric rod — Measuring the inside 
and outside lap — Setting the valve — Fixed cut off engines — 
Variable automatic cut off — Factors affecting the distribution 
of the steam — Why the four valve engine is the most eco- 
nomical—Description of Corliss valves and valve gear and 
directions for adjusting the same. 

Valves and Valve Setting. It goes without saying that 
every man who aspires to be an engineer should en- 
deavor to thoroughly acquaint himself with the princi- 
ples governing the action of valves as well as the details 
of valve setting. But it must be remembered that this 
knowliedge can not be acquired in a day or a week, or 
even months. True, a man maybe able to learn some 
of the alphabet of valve lore in a comparatively short 
time, but the more practical experience he has in the 
work the more will he realize the supreme need of 
mastering all the details of the process. 

The common D slide valve, simple as it appears, is 
capable of furnishing problems over which savants 
have puzzled themselveSc 

The development of the full amount of power of 
which the engine is capable, its efficiency and eco- 
nomical use of steam, and its regular and quiet action 
are, in the largest degree, dependent upon the correct 
adjustment of its valve or valves. 

133 



134 ENGINEERING 

There are many different types of valves for control- 
ling the admission and release of steam to and from the 
cylinders of engines, but the basic principles govern- 
ing the adjustment of all, whether slide, poppet, rota- 
tive, piston, etc., are exemplified in the action of the 
common D slide valve, viz., the admission of the 
steam to the cylinder, its cut off and release, and 
the closure of the exhaust, each and all of which 
events are to take place at the proper moment during 
one stroke of the piston. 

In order to properly perform these important func- 
tions the valve must have lead and lap. The various 
terms relating to valve action are plainly defined 
in Chapter VIII on ''Definitions," and it is unnec- 
essary to repeat them here. If the outside lap is 
increased admission will be later and cut off earlier, 
and if it be desired to keep the lead the same it will be 
necessary to move the eccentric forward, which will 
make the other events, cut off, release, and compres- 
sion, earlier also. If the inside lap is increased the 
result will be an earlier closing of the exhaust and 
increased compression. 

These propositions refer mainly to engines of the 
single valve variety in which one valve controls the 
admission and distribution of the steam for both ends 
of the cylinder. In engines of the four valve type, 
having a separate steam and exhaust valve for each 
end of the cylinder, each individual valve may be 
adjusted independently of the others, as will be 
explained later on, and in the case of engines having 
separate eccentrics, one for the steam and one for the 
exnaust valves, the adjustment becomes still more 
o^rfect. 

\Ve will first study the action of the D slide valve by 



VALVES AND VALVE SETTING 



135 



referring to Fig. 13, which is a sectional view of a 
valve, valve seat and ports. The valve is represented 
at mid travel or in its central position. S P, S P are 
the steam ports, and E P is the exhaust port. The 
projections marked X at each foot of the arch inside 



6 L 




the valve, represent inside lap and may be added to 01 
taken from the inside edges of the valve, according as 
more or less compression is desired. The dotted lines, 
O L, O L represent outside lap. 

Motion is imparted to the valve through the medium 




FIGURE 14. 



of the eccentric. If the valve had neither lap nor lead 
the position of the eccentric on the crank shaft would 
be just 90° or one-quarter of a circle ahead of the 
crank, but as more or less lap as well as lead is 
required, it becomes necessary to move the eccentric 



136 



ENGINEERING 



still farther ahead of the crank, and this farther 
advance is termed angular advance, lap angle for lap 
and lead angle for lead. 

Assuming the piston to be at the end of the stroke 
towards the crank, in other words, the engine to be 




FIGURE 15. 

on the dead center, the first function of the valve is 
lead or admission, illustrated by Fig. 14. Owing to 
the valve having both lap and lead, the position of the 
highest point of the eccentric will be assumed in this 
case to be 120° ahead of the crank, the position of the 
latter being at 0°. 

Exhaust opening has also occurred at the opposite 




FIGURE 



end of the cylinder. The second function is full port 
opening, Fig. 15, the crank having moved through 60° 
and the eccentric is now at 180°, the farthest point of 
its throw in that direction, the valve being at the end 
of its travel. At this point it mig-ht be well to note a 



VALVES AND VALVE SETTING 



137 



matter about which some persons are liable to become 
confused, simple as it is, viz., that the travel of a slide 
valve equals twice the port opening plus twice the out- 
side lap. For instance, suppose the width of each 
steam port to be i}( in. and the outside lap to be i in. 
In Fig. 15 the valve is at the e^xtreme end of its travel 




FIGURE 17. 

towards the right and is about to return. It first 
covers port number one = i^ in. Next it moves to 
mid travel lap number one = 2}{ in. Its next move is 
lap number two = 3^ in., and lastly it uncovers port 
number two = 4^ in., which is its travel. 
To return to the third function of the valve or cut 




FIGURE 18. 

off, Fig. 16. The crank has now traversed 120^ and 
the highest point of the eccentric is at 60° on the 
return circle, a point equivalent to 240° of the circle 
described by the crank. 

The fourth function is when compression begins at 
the head end of the cylinder, Fig. 17. The crank is 



138 



ENGINEERING 



now at 150®, the piston being near the end of the stroke 
and the eccentric has reached 90° of the return circle 
or three-quarters of the crank circle, while the crank 
has still to travel 30° in order to complete the first one- 
half of its circle. At this point we can study the effect 
of inside lap, because if the valve has no inside lap, 
release on the crank end will begin almost at the same 
moment that compression takes place at the head end, 



to^^^ 




i(\ 


-^ / ^^ 


0' I 1 \ 


/^\ 1 / 



/So' 



/^j 



\^ 



9a' 

FIGURE 19. 



but by adding inside lap, compression can be caused 
to take place earlier and release later. 

The next event is admission at the head end of the 
cylinder, Fig. 18. The crank has now arrived at 180°, 
having completed one-half of a revolution; the piston 
is at the end of the stroke, and the eccentric is at 
120° on the return path. Fig. 19 serves to better illus- 
trate the relative positions of the crank pin and 



VALVES AND VALVE SETTING 139 

eccentric during the stroke. The inner circle repre- 
sents the path described by the high point of the 
eccentric, and the large circle that of the crank pin. 
The radius C 2 of the small circle represents the throw 
of the eccentric, and the distance C L is the lap of the 
valve plus the lead. The point of intersection of the 
vertical line, L i, with the eccentric circle locates the 
position of the highest point of the eccentric, and 
the line C B, drawn from the center of the crank shaft 
through this point, indicates the angular advance, 
which in this case is 30° represented by the angle 
ABC. The figures i, 2, 3, 4, 5 indicate the position 
of the high point of the eccentric at the moment of 
each function of the valve. The action of the valve 
can be more graphically illustrated by means of valve 
diagrams, of which there are several different kinds, 
notably the Bilgram and Zeuner. The Zeuner dia- 
gram will be made use of in this instance. 

Fig. 20 shows the total movement of the valve, 
regardless of lap and lead. First draw line C I to 
represent the center line of the engine. Next draw 
line C 4 perpendicular to the line of centers, with C as 
the center of the crank shaft. The radius of the semi- 
circle D, I, 2, 3, 4, 5, 6 equals the radius of eccentri- 
city. Line C D represents the position of the crank 
when the valve is at mid travel or in its central posi- 
tion, D being the location of the crank pin. Referring 
back to Fig. 13 the valve is there shown in its central 
position and supposed to be moving in the direction of 
the arrow in order to admit steam to the crank end of 
the cylinder. Again referring to Fig. 20, draw line 
C A in such a position that the angle ABC will 
equal the angular advance of the eccentric, which we 
will assume in this case to be 30°. This will bring the 



140 



ENGINEERING 



high point of the eccentric at B while the crank, as 
before stated, is at D. Next using line C A as the 
diameter draw a circle about it called the valve circle. 



k 



\3f^ 



.\ 



»i)^i 



-e<' 



.K' 



\ 



FIGURE 20. 



y^"^ 

i^*^ 



Now suppose the crank to be turning in the direction 
of the arrows. At position D the crank line is just 
about to cut into the valve circle, the valve being 
central. When the crank gets to position i the valve 



VALVES AND VALVE SETTING 141 

has moved the distance C E. When the crank is at 2 
the valve has moved the distance C M, and when the 
crank arrives at 3 the valve has moved to the limit of 
its travel from its central position and it now begins 
the return movement. The motion of the valve is 
comparatively slow at this point for the reason that the 
high point of the eccentric is now passing the center 
at 7. The distance the valve has moved backward 
while the crank has moved from 3 to 4 is the distance 
B F, while F C represents its distance from the central 
pos.ition, and G C the same when the crank is at 5. 
When the crank arrives at 6 and its line has left the 
valve circle, the valve is again central. Fig. 20 merely 
shows the movement of the valve through one-half of 
its travel without giving any details regarding port 
openings, cut off, etc. 

In Fig. 21 the influence of outside lap is delineated. 
According to the dimensions of the valve under con- 
sideration the outside lap is one inch. The diagram is 
drawn precisely as in Fig. 20, and in addition strike an 
arc representing the outside lap, using C as the center 
with a radius equal to the outside lap. As before, the 
crank is at D and the valve central. When the crank 
has moved to E and its line cuts the intersection of 
the outside lap and valve circles, the valve has moved 
the distance C H, just equal to the outside lap, and 
the port begins to uncover at this point. Then by the 
time the crank gets to the center, i, the port is open 
the distance L O, which is the lead, in this case }i in. 
This position of the valve is shown in Fig. 14. 

The position of the crank when cut-off takes place is 
ascertained by drawing a line, C G 5, through the inter- 
section of the outside lap and valve circles, where the 
valve is on its return movement (see Fig. 16). Thus 



142 



ENGINEERING 



far no account has been taken of release and compres- 
sion, and in order to determine the position of the 
crank when these events occur it will be necessary to 



// 



tr^ 



sp K- 



vol 



.\ 



>tP 



ii*^ 



V 



.pl^ 



,1^ 









'^e 



FIGURE 21. 



draw the valve circle for the opposite movement of the 
valve, for be it remembered that the movement of the 
valve so far considered has been only one-half of its 



VALVES AND VALVE SETTING 



143 




^°^"-f of cefe,tit,f,t^ 



= / -^ 



'/f 



FIGURE 22. 

travel; that is, it has moved from its central position 
towards the head end of the cylinder and back again. 
We have seen how it has thus performed the functions 



144 ENGINEERING 

of admission, full port opening and cut off for the 
crank end of the cylinder, and now by referring to 
Fig. 22 it will be seen at what point of the stroke th%. 
remaining events, viz., release and compression, 
occur. 

Draw a second valve circle, Fig. 22, diametrically 
opposite the first. Also draw an arc with a radius 
equal to the inside lap, which in this case is assumed 
to be one-half inch. When the crank gets to the 
position 7 its center line cuts the intersection of the 
inside lap and valve circles and release begins. When 
the crank arrives on the center 8, the valve has moved 
the distance C T from central position; but C X of this 
distance has been occupied by the inside lap, therefore 
the lead on the exhaust is represented by the distance 
X T. When the crank on its return stroke arrives at 
the position marked 10, its line again cuts the inter- 
section of the inside lap and valve circles and com- 
pression takes place, as in Fig. 17. By dropping 
perpendiculars from the positions of the crank at i, 5, 
7 and 10 an indicator diagram may be drawn showing 
the performance of an engine with this style of valve. 

Fig. 23 shows the effect of decreasing the angular 
advance, that is, setting the eccentric back towards the 
crank. In this instance the eccentric is set back lo"^, 
thus making the angle of advance 20° instead of 30° as 
before. The full lines represent the new angle, while 
the dotted circles and lines indicate the valve and its 
movements as drawn at first. A shows the original 
point of admission and A' the position of the crank 
when admission takes place with the lesser angle of 
advance. Similarly R and R' show the old and new 
points of release, and C and C the compression. The 
two different points of cut off are also indicated. Ii 



VALVES AND VALVE SETTING 



145 



will be observed that all of these events occur later 
and the lead also is diminished. 

In locomotives, and also in some types of adjustable 
cut off engines, the travel of the valve may be varied 
at will and the effect of decreasing the valve's travel 



\.f 



fi<. 



FIGURE 23. 



is illustrated by Fig. 24, the full lines showing the 
decreased travel and its influence, and the dotted lines 
showing the original. Admission and release occur 
later, while cut off and compression take place earlier, 
and the lead is less. The travel of the valve as indicated 



146 



ENGINEERING 



in Fig. 24 has been decreased one inch, making it 3>^ 
in. in place of 4^ in. as before. 

Fig. 25 shows the result of increasing the outside 
lap. The lap has been increased in this case from i 
in., as originally drawn, to i}( in. as indicated by the 



N ^^J 



W 



.y 



c / 



'r/ 



^^-' 



FIGURE 24 

!ull iii.es, while the dotted lines show the lap as it was 
before being changed. The effect of this change is to 
cause less lead, a later admission and an earlier cut 
off, but compression and release are not affected for 
the reason that these latter events are controlled by 
the inside lap, which has not been changed. 



VALVES AND VALVE SETTING 147 

In Fig. 22 the valve is shown as cutting off the steam 
when the crank has completed 120° or two-thirds of 
the half revolution, but the point of cut off on the indi- 
cator diagram shows that the piston has traveled ^ of 
the stroke. This discrepancy is due to the obliquity 



t^ 



/c^ 



4v)> 



FIGURE 25. 

of the connecting rod, as it will be seen by looking at 
the valve diagram. Fig. 22, that the crank must travel 
farther to complete the stroke from this point than the 
piston does. In order to cause the valve to cut off 
earlier, say at one-half stroke, it will be necessary to 
do one of two things, either to increase the outside 



148 



ENGINEERING 



2 


// /(P" 

\Uod \ 




^ 




J) 


6 


1 














vj 





FIGURE 26. 



lap, which would have a tendency to cause admission 
to occur too late, or the angle of advance may be 



VALVES AND VALVE SETTING 149 

increased sufficient to cause cut off to take place at 
half stroke, but to do this alone would cause admission 
to occur too early. Therefore the proper thing to do 
is to increase both the angle of advance and the out- 
side lap. Fig. 26 shows how this can be done without 
decreasing the travel of the valve. The angle of 
advance, A B C, is now 50°, where before it was 30°, 
as in Fig. 22, 

The valve is central when the crank is at position i; 
the high point of the eccentric being at point 4. The 
outside lap which before was i in. has had ^\ in. added 
to it, making it iy\ in. When the crank gets to D the 
port is just commencing to open, and with the crank 
on the center at 2, the lead is y^ in. 

It will readily be seen at this point that by increasing 
the outside lap still more the lead can be diminished, 
and the point of cut off made still earlier, but this 
would result in a still further reduction of the power of 
the engine, which has already been considerably 
reduced, as shown by the diminished area of the indi- 
cator diagram as compared with the one in Fig. 22. 
When the crank gets to position 3 the valve has 
reached the limit of its travel, and the port is open the 
distance A a, which is as far as the outside lap will 
permit. With the crank at point 4 cut off occurs. But 
with the increased angular advance and the inside 
lap remaining as it was before, viz., ^ in., release 
would occur too early. Therefore it will be nec- 
essary to increase the inside lap sufficient to cause 
release and compression to take place at as near 
the proper points as possible. In this instance ^ 
in. has been added, making the inside lap J^ in., 
and release takes place with the crank at position 5, 
while compression begins at 6. These points may 



150 



ENGINEERING 



also be changed by simply adding to or decreasing 
the inside lap. 

It should be noted that in the foregoing discussion 
of valve gear it is understood that the valve stem 
moves in the same direction as the eccentric rod, that 
is, the direction of motion is not reversed by a rocker 
arm interposed between the eccentric and the valve. 



•cO 






FIGURE 27. 



In case there should be a rocker arm connected so a? 
to reverse the motion and thereby cause the valve to 
move opposite to the eccentric rod, it will be neces- 
sary to set the eccentric behind the crank, as in Fig. 27. 
Most engines are fitted with a rocker arm for trans- 
mitting the motion of the eccentric to the valve stem, 



^ 




FIGURE 28= 



but the usual practice is to attach them so that the 
direction of motion is not reversed, as in Fig. 28 

The first step in the operation of valve setting is to 
place the engine on the dead center, which means that 



VALVES AND VALVE SETTING 151 

the piston is at the end of the stroke, and the centers 
of the main shaft, crank pin and crosshead pin, or, 
wrist pin as it is sometimes called, are in line (see Fig. 
31). When moving the engine to place it on the cen- 
ter it should always be turned in the direction in which 
it is to run. This is to guard against any errors which 
might result from lost motion or looseness in the 
reciprocating parts. Turn the fly wheel around until 
the crosshead is almost to the end of the stroke, say 
within a half inch of it, as at A, Fig. 29. Then with a 




FIGURE 29. 

steel scriber or penknife mark the location of the 
crosshead on the guides A, also provide a secure rest- 
ing place upon the floor of the engine-room for a 
marker to be placed against the rim of the wheel. 
This rest should be firmly fastened to the floor in order 
that its position may not be changed during the opera- 
tion of valve setting. Place the marker against the 
wheel as at B and mark the point with a center punch 
or cold chisel. Next turn the engine carefully until 
the crosshead completes the stroke and moves back on 
the return stroke until the mark A is in line again. 
Make another mark on the rim of the wheel opposite 
the marker at C. This position of the engine is 
shown in Fig. 30, and it will be seen that the crank is 
now as much above the center as it was below in Fig. 



152 



ENGINEERING 



29. Now with a pair of large dividers ascertain the 
middle or half distance between marks B and C and 
put another mark, D, at this point. Then turn the 




FIGURE 30. 

engine a complete revolution until mark D comes 
opposite the pointer, Fig. 31, and the engine will be 
on the true center. 

At this point the question may arise, why not simply 
reverse the motion and back the wheel up until the 
mark D is in line with the marker? The answer is, 




FIGURE 31. 



that while this would undoubtedly save considerable 
labor, yet it would almost certainly result in an error, 
on account of the lost motion of the moving parts 
which would permit of considerable movement of the 
wheel before any movement of the crosshead would 
take place if the wheel was turned back. The result 
would be that when mark D came to be opposite to the 



VALVES AND VALVE SETTING 



153 



pointer, the crank would not be on the true center. 
The next move is to see that the eccentric rod is 
adjusted to the proper length. If there is a rocker 
arm, connect the eccentric rod in its proper place^ 
leaving the valve rod disconnected for the time beings 






- — i> 



Seee/ti/i/c /&<*■ 



j» 



T 



it 



FIGURE 32. 

Then adjust the length of the rod so that when the 
eccentric is turned around on the shaft the rocker arm 
will vibrate equal distances on each side of a plummet 
line suspended through the center of the pin upon 
which the arm turns, as in Fig. 32. Before connecting 



154 



ENGINEERING 



the valve rod the valve should be put in its centra) 
position and marked. To do this it will be necessary 
to first ascertain the outside lap. 

The most accurate method of doing this is to take the 
valve out and measure the distances between the out- 
side edges of the steam ports as at B, Fig. 33. Then 
measure the width of the valve from edge to edge as 
at A. Then A - B -^ 2 = the outside lap. For instance, 
A = 8. 5 in., B-6. 5 in. Then 8.5-6.5-2, and 2 




FIGURE 33. 



divided by 2 = i in., which is the lap. The inside lap 
should also be measured at this point for convenience, 
and the measurements preserved for future reference. 
The inside lap is ascertained by measuring the distance 
between the inside edges of the ports and the distance 
across the arch of the vaive from one inside edge to 
the other (see Fig. 33) and dividing the difference 
by 2. For instance, the distance F is 4 in., and E is 
3 in. ; then ^y~ = • 5 ^^m making the inside lap }4 in. 
To place the valve central, measure the width of the 



VALVES AND VALVE SETTING 155 

outside lap each way from the outside edges of the 
steam ports and mark the points on the valve seat with 
a sharp lead pencil. Then place the valve with edges 
on the marks and it will be central. To insure accu- 
racy measurements snould also be taken from the out- 
side edges of the steam ports to the ends of the seats. 
Having fixed the valve in its central position, replace 
the stem and if it is secured in the valve by nuts, as in 
Fig- 33» care should be taken to leave a little play for 
the valve between the nuts, otherwise it is liable to 
become stuck and held off the seat when it gets hot 
and expands. Make a center punch mark C, on the 
edge of the valve chest directly over the valve stem, 
and placing one leg of a tram or pair of dividers in the 
mark, with the other leg describe a mark on the top of 
the valve as at D, thus marking the valve in its central 
position. 

Now with the rocker arm perpendicular, the eccen- 
tric rod having been previously adjusted, connect the 
valve rod to the rocker, and turn the eccentric to the 
limit of its throw in one direction, and measure 
the distance the valve has traveled from its central 
position. Then turn the eccentric around to its 
extreme throw in the other direction, and if the valve 
travels the same distance from its central position in 
the opposite direction the lengths of the rods are cor- 
rect, but if not correct the necessary change can 
usually be made by shifting the nuts on the valve stem, 
or if the valve is secured to the stem by a yoke the 
change can be made in the rod. 

Having succeeded in getting the correct travel for 
the valve, the next step is to set the eccentric. With 
the engine on the dead center, turn the eccentric 
around on the shaft in the direction in which the 



156 ENGINEERING 

engine is to run, so as to take up all the play in the 
valve stem and other moving parts, and with the tram 
or dividers watch the valve until it has moved away 
from its central position by the amount of its outside 
lap, plus the lead it is desired to give the valve. For 
instance, if the valve has one inch outside lap and the 
lead is to be ^ in., the valve should be moved away 
from its central position i}i in., and also away from 
the end of the cylinder at which the piston is. The 
steam port for that end should now be open }i in., and 
the eccentric should be ahead of the crank one-quarter 
turn plus the angular advance required for the outside 
lap and lead, or if as previously explained, the motion 
of the eccentric is reversed by a rocker arm the eccen- 
tric should be behind the crank by the same amount. 
Tighten the set screws holding the eccentric on to the 
shaft and turn the engine around until it is on the 
opposite center. Then if the lead is the same on each 
center the valve is set correctly. If the lead is not the 
same,, move the valve on the stem toward the end 
having the most lead, a distance equal to one-half the 
difference between the two leads. If the lead as 
equalized is more than is desired, move the eccentric 
back on the shaft until the correct lead opening is 
secured, then tighten the set screws permanently, and 
with a sharp cold chisel make a plain mark on the 
shaft and opposite to this another mark on the 
eccentric. This will save considerable trouble in case 
the eccentric should slip or be accidentally moved 
from its true position at any time. 

Although the common D slide valve as applied to 
stationary engines usually has its point of cut off 
fixed, yet there are many types of variable automatic 
cut off engines with single slide valves of various pat- 



VALVES AND VALVE SETTING 157 

terns, such as box vah'es in which the steam passes 
through the valve, piston valves in which the steam 
either passes through or around the ends of the valve, 
so-called gridiron valves and various other types. 
Such valves are generally applied to high speed 
engines and are actuated by eccentrics which are 
under the control of shaft governors which vary the 
position of the eccentric with relation to the crank 
according to the load that is on the engine, thus regu- 
lating the point of cut off so as to maintain a constant 
speed, while the throttle is kept wide open. While 
the details of setting all the various styles of valves, 
including the corliss or four valve type, differ consider- 
ably from those required in setting the D valve, yet 
the same principles govern the operation, no matter 
what kind of a valve is to be adjusted 

In all types of reciprocating engines the same fac- 
tors affecting the distribution of the steam are present, 
viz., the outside or steam lap affecting admission and 
cut off, and the inside or exhaust lap affecting release 
and compression. While the D valve (and other 
types of single valves) combines these four principal 
factors within itself (that is, two steam laps and two 
exhaust laps), it should be noted that in the four valve 
type of engine the same factors are distributed among 
four valves, each valve performing its own particular 
function in controlling the distribution of the steam 
for the end of the cylinder to which it is attached. 
Also each valve may be adjusted to a certain degree 
independently of the others, and this fact goes far 
towards explaining why engines of this type, with the 
disengaging valve gear, are so much more economical 
in the use of steam than are those with the ordinary 
fixed cut off. Thus, for instance, the steam valves of 



158 



ENGINEERING 



a Corliss engine may be adjusted to cut off the steam 
at any point, from the very beginning up to one-half 
of the stroke, without in the least affecting the release 
or compression because these events are controlled by 
the exhaust valves. 

As the Corliss engine is a prominent and familiar 
type of the four valve detaching cut off engine, and 
embodies the main features of nearly all engines 
belonging to that class, it will be used to illustrate the 
method of setting the valves on a four valve engine. 




FIGURE 34. 



Fig. 34 is a sectional view of the cylinder, steam and 
exhaust chests, and the valve chambers of a corliss 
engine. I and 2 are the steam valves and 3 and 4 the 
exhaust valves. The valves work in cylindrical cham- 
bers accurately bored out, the face of the valve being 
turned off to fit steam light. They are what is termed 
rotative valves, that is, they receive a semi-rotary 
motion from the wrist plate, which in turn is actuated 
by the eccentric. 

In some of the modern improved makes of four 
valve engines there are two eccentrics, one for the 



VALVES AND VALVE SETTING 



159 



steam and the other for the exhaust valves. This 
arrangement permits of still greater latitude in adjust- 
ments for the economical use of steam. 

In Fig. 34 the piston is shown as just ready to begin 
the stroke towards the left. Admission is taking 
place at valve 2 and release at valve 3, valves i and 4 
oeing closed. The arrows show the direction in which 
the valves move. Motion is transmitted from the wrist 
plate to the valves by means of short connecting rods 
and^cranks attached to the valve stems. These rods 




FIGURE 35. 



are, or at least should be, fitted with right and left hand 
:hreads or turn buckles for the purpose of lengthening 
or shortening the rods while setting the valves. 

The valve gear of a corliss engine with a single 
eccentric is shown in Fig. 35. The connections of the 
exhaust valves with the wrist plate are positive, and 
the travel of these valves is fixed, being a constant 
quantity, but the connections of the steam valves with 
the wrist plate are detachable, being under the control 
of the governor. Various designs of releasing mechan- 



160 ENGINEERING 

ism are in use by different builders, but the same gen- 
eral principles govern the operation of all, viz., that 
the valve is quickly opened at the commencement of 
the stroke when the wrist plate has its fastest motion, 
and that the governor trips the releasing meehanism at 
that point in the stroke at which it is desired that cut 
off should take place, and that the valve is then 
quickly closed by means of a vacuum dash pot or, as in 
some types of engines, by a spring. Connection is 
made between the wrist plate and rocker arm by 
means of the hook rod, so-called because it hooks over 
the wrist plate pin, and can easily be disconnected in 
case it is desired to work the valves by hand, as in 
warming up the engine preparatory to starting up. 

Referring to Fig. 35, A is the wrist plate, B and C 
are the dash pot rods, D, D' the dash pots and H R the 
hook rod. G and G' represent the governor rods, and 
the figures I, 2, 3 and 4 indicate the valve rods with 
turn buckles for changing their lengths. 

As in setting the slide valve, the first requisite in 
setting Corliss valves is to put the engine on the cen- 
ter, the method of doing which has been fully 
described. Next adjust the length of the hook rod, if 
it is adjustable, if not, then the eccentric rod so that 
the wrist plate will vibrate equal distances each way 
from its central position which is marked on top of 
the hub. (See Fig. 36.) It will be noticed that there 
are four marks, A, B, C and D. Marks A and B are on 
the hub of the wrist plate and the stationary flange 
against which it turns, and when they are in line, indi- 
cate that the wrist plate is central. Marks C and D 
are on the stationary flange at equal distances each 
way from B, and when the engine is running mark A 
should travel to the right until it is in line with D and 



VALVES AND VALVE SETTING 



161 



to the left until in line with C, or it may happen that 
A will travel past C and D or perhaps not quite to 
them, but which ever it does, it should stop at equal 
distances from them. This adjustment should be care- 
fully made before setting the valves, because if any 




FIGURE 36. 



change is made in the lengths of the eccentric rod ol 
hook rod after the valves are once set it will seriouslj 
affect the action of all the valves. 

The method of adjusting the rocker arm so that it 
will vibrate correctly has been already described and 
it is very desirable that its travel should be equidistant 



162 



ENGINEERING 



in either direction from a vertical position, but if it is 
Tound that the hook rod is non-adjustable as to length 
and that the wrist plate still vibrates too far in one 
direction, then the adjustment must be made on the 
length of the eccentric rod, which can be screwed into 
or out of the strap. The vibration of the wrist plate 
should then be tested by turning the eccentric around 
on the shaft in the direction the engine is to run. 
When this is found to be correct the next step is to 
remove the back bonnets from the valve chambers. 
Fig. 37 represents one of the steam valves and Fig. 38 




FIGURE 37 



one of the exhaust valves, each with back bonne' 
removed, showing the ends of the valves. 

The working edges of the valves, as well as the 
ports of a Corliss engine, cannot be seen when the 
valves are in place, owing to the fact that the circular 
ends of the valves fill the spaces at the ends of the 
valve chambers, but certain marks will be found on the 
ends of the valves, and corresponding marks on the 
faces of the chambers which serve as a guide in set- 
ting the valves. Referring to Fig. 37, mark V on the 
end of the valve is in line with the edge of the valve, 
and P indicai^es the edge of the porr. The same let* 



VALVES AND VALVE SETTING 



168 



ters apply to Fig. 38. Having removed the bonnets and 
found the marks, temporarily secure the wrist plate in its 
central position by tightening one of the set screws on 
the eccentric. Then connect the valve rods, adjusting 
their lengths so that the steam valves will have from 
.V16 to }i in. lap, and the exhaust valves from 1/16 to 
j4 in. lap. These figures vary according to the size of 
the engine, the smaller figures being for small size en- 
gines and the larger figures apply to large sizes. 





FIGUKE 38. 



In adjusting the steam valves be sure and note the 
direction in which they turn to open. In most corliss 
engines the arm of the crank to which the valve rod is 
connected extends downwards from the valve stem, as 
in Fig. 35. This Vv^ill cause the valve to move towards 
the wrist plate in opening. After the valve rods have 
been properly adjusted as to length, place the engine 
on either center by the method previously explained and 
move the eccentric around on the shaft in the direction 
in which the engine is to run until it is far enough ahead 
of the crank to allow the steam valve the proper amount 
of lead opening, which will vary according to the size of 
tfte engme. Table 7 gives the lap and lead for various 



164 



ENGINEERING 



sizes of corliss engines from 8 to 36 in. bore. Having 
tightened the eccentric set screws, turn the engine around 
to the opposite center and note whether the lead is the 
same on each end. If there is a difference it can gen- 
erally be equalized by slightly altering the length of one 
of the valve rods. The valves should also be adjusted 
by means of the indicator at the first opportunity, as that 
is the only absolutely correct method. 

TABLE 7 
TABI.E FOR Setting Cori^iss Vai^vks. 



Diameter of 


Lap of Steam 


Lap of Exhaust 


Lead of Steam 


Cylinder. 


Valves. 


Valves. 


Valves. 


8 


3-lH 


1-16 


1-32 


10 


3-16 


1-16 


1-32 


12 


3-16 


1-16 


1-32 


14 


1-4 


1-8 


1-32 


16 


1-4 


1-8 


1-32 


18 


1-4 


1-8 


1-32 


20 


1-4 


1-8 


1-32 


22 


5-16 


3-16 


3-64 


24 


5-16 


3-16 


3-64 


26 


5-16 


3-16 


3-64 


28 


5-16 


3-16 


3-64 


30 


5-16 


3-16 


3-64 


32 


3-8 


1-4 


1-16 


34 


3-8 


1-4 


1-16 


36 


3-8 


1-4 


1-16 



The next point to receive attention is the adjustment 
of the lengths of the horizontal rods extending from 
the governor to the releasing mechanism, so that the 
steam valves will cut off at equal points in the stroke. 
This is done by raising the hook rod clear of the wrist 
plate pin, and with the bar provided for the purpose 
move the wrist plate to either one of its extreme posi- 
tions as shown by the marks on the hub (see Fig. 36) 



VALVES AND VALVE SETTING 165 

and holding it in this position adjust the length of the 
governor rod for the steam valve (which will then be 
wide open) so that the boss or roller which trips the 
releasing mechanism is just in contact, or within ^V '*"• 
of it. Then move the wrist plate to the other extreme 
of its travel and adjust the length of the other rod in 
the same manner. To prove the accuracy of the 
adjustment, raise the governor balls to their medium 
position, or about where they would be when the 
engine is running at its normal speed and block them 
there. Then having again connected the hook rod to 
the wrist plate, turn the engine around in the direction 
in which it is to run, and when the valve is released, 
measure the distance upon the guide that the crosshead 
has traveled from the end of the stroke. Now con- 
tinue to turn the engine in the same direction until the 
other valve is released, and measure the distance that 
the crosshead has traveled from the opposite end of 
the stroke, and if the cut off is equalized these two 
distances will be the same. If there is a difference, 
lengthen one rod and shorten the other until the point 
of cut off is the same for both ends. 

The lengths of the dash pot rods should also be 
adjusted so that when the plunger is at the bottom of 
the dash pot the valve lever will engage the hook. 

After all adjustments have been made tighten the 
lock nuts on all the rods. 

Questions 

1. What important features in the operation of an 
engine are dependent upon a correct adjustment of the 
valves? 

2. How many different types of valves are there in 
general use? 



166 ENGINEERING 

3. What are the basic principles governing the 
adjustment of the valves of an engine? 

4. Name two important functions of a valve. 

5. What is the effect of increasing the outside lap? 

6. What is the result of increasing the inside lap? 

7. What advantage has an engine of the four valve 
type over one with but a single valve? 

8. Suppose a valve had neither lap nor lead, what 
would be the position of the eccentric in relation to 
the crank? 

9. What is meant by the term "angular advance/* 
and why is it necessary? 

10. What is the first function of the valve at the 
commencement of the stroke? 

11. What is the second function? 

12. What is the travel of a slide valve equivalent to? 

13. What is the third function of the valve? 

14. What is the fourth function? 

15. What will be the effect if a valve has no inside 
lap? 

16. How can the action of a slide valve be graphically 
illustrated? 

17. Name the two most commonly used valve dia- 
grams. 

18. What is meant by the expression, ''radius of 
eccentricity"? (See Chapter VIII.) 

19. Why must a valve have outside lap? 

20. What is the object in giving a valve inside 
lap? 

21. What is the result of decreasing the angular 
advance? 

22. What will be the result if the travel of the valve 
is decreased? 

.>3. W^hat three changes must be made in order to 



VALVES AND VALVE SETTING 167 

cause an earlier cut off in an engine that has a fixed 
cut off? 

24. What is the first step in the operation of valve 
setting? 

25. When is an engine on the dead center? 

26. What precautions should be observed in turning 
an engine to place it on the center? 

27. Why is this necessary? 

28. Describe briefly the process of placing an engine 
on the dead center. 

29. What is the next move in the routine of valve 
setting? 

30. What should be done with the valve before con- 
necting it to the valve rod? 

31. How may the outside lap be ascertained? 

32. How is the amount of inside lap found? 

33. Should the valve be rigidly secured to the stem? 

34. Describe the proper method of adjusting the 
length of the rod in order that the valve may travel 
correctly. 

35. How is the correct position of the eccentric on 
the shaft ascertained? 

36. If the lead is not the same at each end of the 
stroke, how may it be equalized? 

37. If there is more lead than is desired, how may it 
be decreased? 

38. What is the function of a shaft governor in rela- 
tion to the eccentric? 

39. Why is the four valve type of engine more eco- 
nomical in the use of steam than the single valve type 
with fixed cut off? 

40. How should the wrist plate be adjusted? 

41. If the wrist plate does not vibrate correctly what 
will be the result? 



168 ENGINEERING 

42. How should the rods connecting the governor 
with the releasing mechanism be adjusted? 

43. How may this adjustment be tested? 

44. How should the dash pot rods be adjusttd as to 
length? 



CHAPTER VIl 

THE INDICATOR 

The indicator — Its invention and improvement — Principles 
governing its operation — Diagrams from condensing and non- 
condensing engines — Sizes of springs to be used for various 
pressure — Reducing mechanism — The reducing wheel — 
Different forms of pendulum reducing motion — Brumbo pul- 
ley — The pantograph — Attaching the indicator — Parts of the 
cylinder to which indicator pipes should not be connected — 
Care of the instrument — Cleaning, oiling, etc. — Directions for 
taking diagrams. 

The Indicator. One of the greatest aids to the eco* 
nomical operation of the steam engine is the indicator, 
and it is the privilege of every engineer to have at least 
an elementary, if not a thorough knowledge of its prin- 
ciples and working. The time devoted to the study of 
the indicator, and in its application to the engine, is 
time well spent, and in the end will well repay the 
student of steam engineering. 

Inventor, The indicator was invented and first ap- 
plied to the steam engine by James Watt, whose restless 
genius was not satisfied with a mere outside view of bis 
engine as it was running, but he desired to know more 
about the action of the steam in the cylinder, its pressure 
at different portions of the stroke, the laws governing its 
expansion after being cut off, etc. Watt's indicator, 
although crude in its design and construction, con- 
tained embodied within it all of the principles of the 
modern instrument. 

Principles. These principles are: 

First. The pressure of the steam in the engine 

169 



170 



ENGINEERING 



cylinder throughout an entire revolution, against a 
small piston in the cylinder of the indicator, which in 
turn is controlled or resisted in its movement by sl 




SECTIONAL VIEW CROSBY INDICATOR. 

spring of known tension, so as to confine the stroke of 
the indicator piston within a certain small limit. 

Second. The stroke of the indicator piston is com- 
municated by a multiplying mechanism of levers and 
parallel motion to a pencil moving in a straight line. 
The distance through which the pencil moves being 



THE INDICATOR 



171 



governed by the pressure in the engine cylinder and 
the tension of the spring. 

Third. By the intervention of a reducing mechan- 
ism and a strong cord, the motion of the piston of the 
engine throughout an entire revolution is communi- 
cated to a small drum attached to and 
forming a part of the indicator. The 
movement of the drum is rotative and 
in a direction at right angles to the 
movement of the pencil. The forward 
stroke of the engine piston causes the 
drum to rotate through part of a revo- 
lution and at the same time a clock 
spring connected within the drum is 
wound up. On the return stroke the 
motion of the drum is reversed and the 
tension of the spring returns the drum 
to its original position and also keeps 
the cord taut. 

To the outside of the drum a piece of 
blank paper of suitable size is attached and held in place 
by two clips. Upon this paper the pencil in its motion 
up and down traces a complete diagram of the pressures 
and other interesting events transpiring within the en- 
gine cylinder during the revolution of the engine. In 
fact the diagram traced upon the paper is the compound 
result of two concurrent movements. First, that of the 
pencil caused by the pressure of the steam against 
the indicator piston; second, that of the paper drum 
caused by, and coincident with, the motion of the 
engine piston. The upper end of the indicator cylin- 
der is always open to the atmosphere, the steam acting 
only upon the underside of the small piston, and when 
the cock connecting the cylinders of the engine and 




CROSBY INDI- 
CATOR SPRING. 



172 ENGINEERING ' 

indicator is closed, both ends of the indicator cylinder 
are open to atmospheric pressure, and the pencil then 
stands at its neutral position. If now the pencil is 
held against the paper and the drum rotated either by 
hand or by connecting it with the cord, a horizontal 
line will be traced. This line is called the atmospheric 
line, meaning the line of atmospheric pressure, and it 
is a very important factor in the study of the diagram. 

If the engine is a non-condensing engine the pencil 
in tracing the diagram will, or at least, should not fall 
below the atmospheric line at any point, but will on 
the return stroke trace a line called the line of back 
pressure at a distance more or less above the atmos- 
pheric line and very nearly parallel with it. If the 
engine is a condensing engine the pencil will drop 
below the atmospheric line while tracing the line of 
back pressure on the diagram, and the distance this 
line is below the atmospheric line will depend upon 
the number of inches of vacuum in the condenser. 

As before stated, the length of stroke of the indi- 
cator piston and the pencil movement as well is 
controlled by a spiral steel spring which acts in resist- 
ance to the pressure of the steam. These springs are 
made of different tensions in order to be suitable to 
different steam pressures and speeds, and are numbered 
20, 40, 60, etc., the number meaning that a pressure per 
square inch in the engine cylinder corresponding to the 
number on the spring will cause a vertical movement of 
the pencil through a distance of one inch. Thus, if a 
number 20 spring is used and the pressure in the 
cylinder at the commencement of the stroke is 20 lbs. 
per square inch, the pencil will be raised one inch, or 
if the pressure is 30 lbs. , the pencil will travel i}^ in., 
And if there is a vacuum of 20 in. in the condenser, 



THE INDICATOR 



173 



the pencil will drop y^ in. below the atmospheric line 
for the reason that 20 in. of vacuum corresponds to a 




IMPROVED TABOR INDICATOR WITH OUTSIDE CONNECTED SPRIN.f 
4.SHC^OFT MFG. CO., N. Y. 



pressure of about lo lbs. less than atmospheric pressure 
or an absolute pressure of about 4 lbs. If a 60 spring 
^« used a pressure of 60 lbs. in the engine cylinder will 



i74 



ENGINEERING 



be required to raise the pencil one inch, or 90 lbs. to 
raise it lyi in. 

The Ashcroft Manufacturing Co. of New York, 
makers of the well known Tabor indicator, have 
recently introduced a new feature in indicator work by 
connecting the spring on top of the cylinder and in 
plain view of the operator. This arrangement removes 
the spring from the influence of direct contact with the 





FIGURE 39. 



FIGURE 40. 



steam, and it is subject only to the temperature of the 
surrounding atmosphere. It is claimed that as a result 
of this the accuracy of the spring is insured and that 
no allowance need to be made in its manufacture for 
expansion caused by the high temperature to which it 
is subject w^hen located within the cylinder. Another 
good feature of this design is, that the spring can be 
easily removed without disconnecting any one part of 
the instrument in case it is desired to changfe sprine^s. 



THE INDICATOR 175 

A cut of the improved instrument is herewith pre- 
sented. 

Fig. 39 is a sectional view of the American Thomp- 
son improved indicator. Fig. 40 shows the spring. 
Fig. 41 is a three way cock for attaching the indicator 
to the cylinder. 

Reducing Mechanism. Probably the only practically 
universal mechanism for reducing the motion ot the 
crosshead is the reducing wheel, a device in which, by 




FIGURE 41. 

the employment of gears and pulleys of different diam- 
eters, the motion is reduced to within the compass of 
the drum, and the device is applicable to almost any 
make of engine, whether of high or low speed. Some 
makers of indicators attach the reducing wheel directly 
to the indicator, thus producing a neat and very con- 
venient arrangement. Fig. 42 shows the indicator 
complete with reducing wheel attached. 

One of the most accurate and easily applied devices 
for reducing the motion of the piston is the wooden 



176 



ENGINEERING 



pendulum in *ts various forms. (See Figs. 43, ^^, j id 
45.) It consists of a flat strip of pine or other light 
wood of a length net less than one and a half times the 
stroke of the engine, and if made longer it will be 
better. It should be from 3.^ to ^ in. thick and have 
an average width of ab^ut 4 in. If the enp-^ne to be 




FIGURE 42. 



indicated is horizontal the bar or pendulum is to b^ 
pivoted at a fixed point directly above and in line with 
the side of the crosshead, as that is generally the most 
convenient point of attachment. The pivot can be 
fixed to a permanent standard bolted to the frame of 
the engine (Fig. 46). or it may be secured to the ceil- 



THE INDICATOR 



177 



ing of the room or even to a post fastened to the floor. 
If the engine is vertical the bar can be pivoted to the 
wall of the room or a strong post firmly secured to the 
floor. The connection with the crosshead is best 
accomplished by means of a short bar or link. A con- 
venient length for this bar is one-half the stroke of the 
engine. To locate the correct point for the pivot, 





FIGURE 43. 



assuming the length of the short bar to be one-half the 
length of the stroke, proceed as follows: 

Place the engine on the center with the crosshead at 
the end of the stroke towards the crank. Then having 
previously bored a hole for the pivot in one end of the 
pendulum bar and in the other end a hole for connect- 
ing with the link, suspend the pendulum by a tem- 
porary pin, as a large wood screw, directly above and in 



178 



ENGINEERING 



line with the stud or bolt hole which has previously 
been tapped into the crosshead at any convenient 
point. The pendulum should be temporarily sus- 
pended at such a height that when it hangs perpendic- 
ular the hole in its lower end will line up accurately 
with the hole or stud in the crosshead. Now swing 
the pendulum in either direction a distance equal to 
the length of the link (one-half the stroke of the 




FIGURE 44. 



engine) from the crosshead connection and note the 
distance that the bottom hole is above a straight edge 
laid horizontal and in line with the center of the stud 
m the crosshead. This will give the total vibration of the 
free end of the link from a line parallel with the line 
of the engine and the permanent location of the pivot 
should be one-half of this distance below the tem- 
porary point of suspension. This will allow the iink 



THE INDICATOR 



179 



to vibrate equally above and below the center of its 
connection with the crosshead. Fig. 47 shows a com- 
plete connection of this character. 

Sometimes the end is slotted and thus directly con- 
nected to the stud in the crosshead, dispensing with 
the link. In this case it is necessary to locate the 
j^ivot at a point perpendicular to the center of travel 
of the stud in the crosshead. (See Fig. 43.) The link 




FIGURE 45. 



connection is to be preferred, however. The cord can 
be attached to the pendulum at a point near the pivot 
which will give the desired length of diagram. This 
point can be determined by multiplying the length of 
the pendulum by the desired length of diagram and 
dividing the product by the stroke. For convenience 
these terms should be expressed in inches. Thus, 
SLSSume stroke of engine to be 48 in., length of pe/i^la- 



180 



ENGINEERING 



lum i^ times length of stroke = "ji in. Desired length 
of diagram 3 in. Then 72 x 3 -5- 48 = 4.5 in., which i? 




FIGURE 46. 

the distance from center of pivot to point of connec- 
tion for the cord. This can be either a small hole 




FIGURE 47. 



THE INDICATOR 



181 



bored through the pendulum or a wood screw to which 
the cord can be attached. From this point the cord 
should be led over a guide pulley located at such 
height that when the pendulum is vertical the cord 
will leave it at right angles. After leaving the guide 
pulley the cord can be carried at any angle desired. 
The Brumbo Pulley, Another method of connecting 
the cord to the pendulum is to run the cord over a 
grooved segment, called a Brumbo pulley, connected 




FIGURE 48. 



with the pivoted end of the pendulum (Fig. 48), but 
with this arrangement, owing to the curved travel of 
the pendulum, there is greater liability to distortion of 
the diagram than in the first method. In case it is 
desired to use the Brumbo pulley, the radius of the 
segment can be found by the same process as that 
used for finding the point for connecting the cord 
directly to the pendulum. 

One of the neatest and most easily applied devices 



18£ 



ENGINEERING 



for reducing the motion of the crosshead is the panto- 
graph. (See Fig. 49.) No dimensions are essential 
except that it shall be made reasonably strong of some 
light, tough variety of wood, and that the pins and 
holes be nicely fitted to each other so that while the 
movement may be free there shall at the same time 
not be too much lost motion. The pantograph should 
be of such capacity that it will just close up nicely 
when the engine is at mid stroke and open out nicely 
when at its extreme travel. The two ends, C and D, 




FIGURE 49. 

are each to be fitted with a pin extending through far 
enough so that pin C can be hooked into a hole or 
socket on the crosshead, while pin D rests in a socket 
in the top of a post secured to the floor at a 
point opposite the center of travel of the crosshead 
and of such height as will allow the pantograph to lie 
in a horizontal position. Also the distance of the post 
from the guides must be adjusted so as to allow the 
device to close up at mid stroke and open out at full 
stroke without any straining of the parts. The point 
F of connection for the cord will always have a motion 



THE INDICATOR 



183 



parallel with, and simultaneous with, that of the cross- 
head; the pin to which the cord is attached can be set 
in any one of the holes that will give the desired 
length for the diagram. The motion given by this 
device is accurate, although it may become necessary 




CROSBY REDUCING WHEEL. 



in some cases, especially with long stroke engines, to 
introduce a guide pulley to carry the cord from the 
pantograph. 

Attaching the Indicator. The cylinders of most 
engines at the present time are drilled and tapped for 



184 ENGINEERING 

indicator connections before they leave the shop, 
which is eminently proper, as no engine builder, or 
purchaser either, should be satisfied with the perform- 
ance of a new engine until after it has been accurately 
tested and adjusted with the indicator. 

The main requirements in these connections are that 
the holes shall not be drilled near the bottom of the 
cylinder where water is likely to find its way into the 
pipes, neither should they be in a location where 
the inrush of steam from the ports will strike them 
directly, nor where the edge of the piston is liable to 
partly cover them when at its extreme travel. An 
engineer before he undertakes to indicate an engine 
should satisfy himself that all these requirements are 
fulfilled. Otherwise he is not likely to obtain a true 
diagram. The cock supplied with the indicator is 
threaded for one-half inch pipe and unless the engine 
has a very long stroke it is the practice to bring the 
two end connections together at the side or top of the 
cylinder and at or near the middle of its length, where 
they can be connected to a three way cock. The pipe 
connections should be as short and as free from elbows 
as possible in order that the steam may strike the 
indicator piston as nearly as possible at the same 
moment that it acts upon the engine piston. 

The work of taking diagrams is very much simplified 
by having both ends of the cylinder connected to one 
common tee or a three way cock as above described, 
but for long stroke engines there should be two indi- 
cators, one for each end and the diagrams should be 
taken simultaneously if it is desired to adjust the 
valves by the indicator. In this case an assistant 
would be required to manipulate one of the instru- 
ments. 



THE INDICATOR 185 

The pipes should always be thoroughly blown out 
by allowing the steam to blow through the open cock 
during several revolutions of the engine, before con- 
necting the indicator. If this is not done there is a 
moral certainty that grit and dirt will get into the 
cylinder of the indicator, where the pressure of the 
least atom of grit will cause the delicate instrument to 
work badly. 

^Selecting a Spring. The proper number of spring to 
use depends upon the boiler pressure in the case of an 
automatic cut off engine, but for an engine with a 
fixed cut off and throttling governor the number of the 
spring to be selected will depend upon the initial 
pressure in the cylinder. A convenient rule is to 
select a spring numbered one-half as high as the pres- 
sure; for instance, if the boiler pressure is 80 lbs., use a 
No. 40 spring, which will give a diagram 2 in. in height. 

Care of the Instrument. The indicator should be 
cleaned and oiled both before and after using. The 
best material for wiping it is a clean piece of old soft 
muslin of fine texture, as there is not so much liability 
of lint sticking to or getting into the small joints. Use 
good clock oil for the joints and springs, and before 
taking diagrams it is a good practice to rub a small 
portion of cylinder oil on the piston and the inside of 
the cylinder, but when about to put the instrument 
away these should be oiled with clock oil also. None 
but the best cord should be used for connecting the 
paper drum with the reducing motion, as a cord that is 
liable to stretch will cause trouble. Suitable cord and 
also blank diagrams can generally be secured from 
firms manufacturing and selling indicators. After the 
indicator has been screwed on to the cock connecting 
with the pipe, the cord must be adjusted to the proper 



186 ENGINEERING 

length before hooking it on to the drum. This must 
be done while the engine is running, by taking hold 
of the loop on the cord connected with the reducing 
motion with one hand, and with the other hand grasp 
the hook on the short cord attached to the drum, then 
by holding the two ends near each other during a revo- 
lution or two it will be seen whether the long cord 
needs to be shortened or lengthened. 

The length of the diagram is determined by the 
point of connection of the cord to the pendulum as has 
been heretofore explained. Care should be exercised 
in placing the paper on the drum, to see that it is 
stretched tight and firmly held by the clips. The 
pencil point having been first sharpened by rubbing it 
on a piece of fine emery cloth or sand paper should be 
adjusted by means of the pencil stop with which all 
indicators should be provided, so that it will have just 
sufficient bearing against the paper to make a fine, 
plain mark. If the pencil bears too hard on the paper 
it will cause unnecessary friction and the diagram will 
be distorted. The best method of ascertaining this 
fact and also whether the travel of the drum is equally 
divided between the stops, is to place a blank diagram 
on the drum, connect the cord and while the engine 
makes a revolution hold the pencil against the paper. 
Then unhook the cord, remove the paper and if the 
travel of the drum is not divided correctly it can be 
changed. 

Having thus arranged all the prelimimary details, 
place a fresh blank on the drum, being careful to keep 
the pencil out of contact with it, connect the cord, 
open the cock admitting steam to the indicator and 
after the pencil has made a few strokes to allow the 
cylinder to become warmed up, then gently swing it 



THE INDICATOR 187 

around to the paper drum and hold it there while the 
engine makes a complete revolution. Then move the 
pencil clear of the paper, close the cock and unhook 
the cord. Now trace the atmospheric line by holding 
the pencil against the paper while the drum is revolved 
by hand. This method of tracing the atmospheric )'ne 
is preferable to that of tracing it immediately after 
closing the cock and while the drum is still being 
moved by the engine, for the reason that there is not 
so much liability of getting the atmospheric line too 
high owing to the presence of a slight pressure of 
steam remaining under the indicator piston for a 
second or two just after closing the cock; also the line 
drawn by hand will be longer than one drawn while 
the drum is moved by the motion of the engine and 
will therefore be more readily distinguished from the 
line of back pressure. 

Having secured a truthful diagram, it now remains 
to take as many as are desired, and if the object is to 
set the valves of the engine, the diagrams from each 
end of the cylinder should follow each other as quickly 
as possible in order that the conditions of load and 
steam pressure may be the same. When the indicator 
is connected so that diagrams can be taken from both 
ends without changing it, the above conditions can 
generally be realized. But if diagrams can only be 
taken from one end at a time, the only way to arrive 
at correct conclusions in relation to the adjustment of 
the valves will be to see that the boiler pressure is 
practically the same at the time of taking diagrams 
from either end and that the position of the governor 
is also the same, assuming that the load on the engine 
is practically constant. This applies of course to an 
automatic cut off. 



188 ENGINEERING 

As soon as the diagrams are taken the following 
data should be noted upon them: The end of the 
cylinder, whether head or crank; boiler pressure; and 
time when taken. Other data can be added after- 
wards. If the engine is an automatic cut off of the 
Corliss type and the point of cut off on one end does 
not coincide with the other, the difference can gener- 
ally be adjusted while the engine is running by chang- 
ing the length of the rods extending from the governor 
to the tripping device. These rods are, or should be, 
fitted with right and left threads on the ends for this 
purpose. Any changes in the valves, such as giving 
them more lead, compression, etc., and which neces- 
sitates changing the length of the reach rods connect- 
ing them with the wrist plate, will have to be made 
while the engine is stopped, although with slow speed 
engines and the exercise of caution it is possible to 
make alterations in these rods while the engine is 
running. 

Questions 

1. What instrument is a necessary part of an 
engineers outfit? 

2. Who invented the indicator? 

3. Name the principles governing the action of the 
indicator. 

4. What will a truthful diagram from a steam 
cylinder show? 

5. Does the steam act upon both sides of the indi- 
cator piston? 

6. What does the atmospheric line show? 

7. Is this line important in the study of the dia- 
gram? 

8. Where should the line of back pressure appear in 
a diagram from a non-condensing engine? 



THE INDICATOR 189 

9. Where will the line of back pressure appear on a 
diagram from a condensing engine? 

10. What controls the length of stroke of the indi- 
cator piston? 

11. What does the number on the spring mean? 

1^2. What is one of the most convenient appliance^ 
for reducing the motion of the crosshead within the 
compass of the drum? 

13. What other appliances besides the reducing 
wheel may be employed for this purpose? 

14. What is a Brumbo pulley? 

15. What are the main requirements in indicator 
connections? 

16. What should be done with the pipes before 
attaching the indicator? 

17. Upon what does the selection of the scale of 
spring depend? 

18. What is a convenient rule to be observed in the 
selection of a spring? 

19. What is the best method of tracing the atmos- 
pheric line? 

20. What data should be noted on the diagram as 
soon as it is taken? 



CHAPTER VIII 

DEFINITIONS AND TABLES 

Definition of words, terms and phrases — Table of* hyperbolic 
logarithms — Table of areas and circumferences of circles. 

In order to facilitate the study and analysis of indi- 
cator diagrams, the following definitions of technical 
terms, some of which have already been explained in 
another part of this book, are here given. 

Absolute pressure. Pressure reckoned from a perfect 
vacuum. It equals the boiler pressure plus the atmos- 
pheric pressure. 

Boiler pressure or gauge pressure. Pressure above the 
atmospheric pressure as shown by the steam gauge. 

Initial pressure. Pressure in the cylinder at the be- 
ginning of the stroke. 

Termijial pressure {T. P.). The pressure that would 
exist in the cylinder at the end of the stroke provided 
the exhaust valve did not open until the stroke was 
entirely completed. It may be graphically illustrated 
on the diagram by extending the expansion curve by 
hand to the end of the stroke. It is found theoretically 
by dividing the pressure at point of cut off by the ratio 
of expansion. Thus, absolute pressure at cut off = lOO 
lbs., ratio of expansion = 5; then 100 -^ 5 = 20 lbs., abso- 
lute terminal pressure. 

Mean effective pressure {M. E. P.). The average 
pressure acting upon the piston throughout the stroke 
minus the back pressure. 

Back pressure. Pressure which tends to retard the 
forward stroke of the piston. Indicated on the dia- 
gram from a non-condensing engine by the height of 

190 



DEFINITIONS AND TABLES 191 

the back pressure line above the atmospheric line. In 
a condensing engine the degree of back pressure is 
shown by the height of the back pressure line above 
an imaginary line representing the pressure in the 
coridenser corresponding to the degree of vacuum in 
inches, as shown by the vacuum gauge. 

Total or absolute back pressure, in either a condensing 
or non-condensing engine, is that indicated on the 
diagram by the height of the line of back pressure 
above the line of perfect vacuum. 

Ratio of expansion. The proportion that the volume 
of steam in the cylinder at point of release bears to 
the volume at cut off. Thus, if the point of cut off is 
at one-fifth of the stroke, and release does not take 
place until the end of the stroke, the ratio of expan- 
sion, or in other words, the number of expansions, is 
5. When the T. P. is known the ratio of expansion 
may be found by dividing the initial pressure by 
the T. P. 

Wire drawing. When through insufficiency of valve 
opening, contracted ports, or throttling governor, the 
steam is prevented from following up the piston at full 
initial pressure until the point of cut off is reached, it 
is said to be wire drawn. It is indicated on the dia- 
gram b}^ a gradual inclination downwards of the steam 
line from the admission line to the point of cut off. 
Too small a steam pipe from boiler to engine will also 
cause wire drawing and fall of pressure. 

Condenser pressure may be defined as the pressure 
existing in the condenser of an engine, caused by the 
lack of a perfect vacuum. As, for instance, with a 
vacuum of 25 in. there will still remain the pressure 
due to the 5 in. which is lacking. This will be about 
2.5 lbs. 



192 ENGINEERING 

Vacuum, That condition existing within a closed 
vessel from which all matter, including air, has been 
expelled. It is measured by inches in a column of 
mercury contained within a glass tube a little over 30 
in. in height, having its lower end open and immersed 
in a small open vessel filled with mercury. The upper 
end of the glass tube is connected with the vessel in 
which the vacuum is to be produced. When no 
vacuum exists the mercury will leave the tube and fill 
the lower vessel. When a vacuum is maintained in 
the condenser, or other vessel, the mercury will rise in 
the glass tube to a height corresponding to the degree 
of vacuum. If the mercury rises to the height of 30 
in. it indicates a perfect vacuum, which means the 
absence of all pressure within the vessel, but this con- 
dition is never realized in practice; the nearest 
approach to it being about 28 in. 

For purposes of convenience the mercurial vacuum 
gauge is not generally used, it having been replaced 
by the Bourdon spring gauge, although the mercury 
gauge is used for testing. 

The vacuum in a condenser is generally maintained 
by an air pump, although it can be produced and 
maintained by the mere condensation of the steam as 
it enters the condenser by allowing a spray of cold 
water to strike it. The steam when it first enters the 
condenser drives out the air and the vessel is filled 
with steam which, when condensed, occupies about 
1,600 times less space than it did before being con- 
densed, hence a partial vacuum is produced. 

While the vacuum in a condenser cannot be consid- 
ered as power at all, yet it occupies the anomalous 
position of increasing, by its presence, the capacity of 
the engine for doing work. Th^s is owing to the fact 



DEFINITIONS AND TABLES 19.^ 

that the atmospheric pressure or resistance which is 
always ahead of the piston in a non-condensing engine 
is, in the case of a condensing engine, removed to a 
degree corresponding to the height of the vacuum, thus 
making available just so much more of the pressure 
behind the piston. Thus, if the average steam pres- 
sure throughout the stroke is 30 lbs. and there is a 
vacuum of 26 in. maintained in the condenser, there 
will be 13 lbs. of resistance per square inch removed 
from in front of the piston, thus making available 
30-h 13 = 43 lbs. pressure per square inch. 

Absolute zero has been fixed by calculation at 461.2° 
below the zero of the Fahrenheit scale. 

Piston displacement. The space or volume swept 
through by the piston in a single stroke. Found by 
multiplying the area of piston by length of stroke. 

Piston clearance. The distance between the piston 
and cylinder head when the piston is at the end of the 
stroke. 

Steam clearance, ordinarily term^ed clearance. The 
space between the piston at the end of the stroke and 
the valve face. It is reckoned in per cent, of the total 
piston displacement. 

Horse power {^H. P.). 33,000 pounds raised one foot 
high in one minute of time. 

Indicated horse power {I. H. P.). The horse power 
as shown by the indicator diagram. It is found as 
follows: 

Area of piston in square inches x M. E. P. x piston 
speed in feet -f- 33,000. 

Piston speed. The distance in feet traveled by the 
piston in one minute. It is the product of twice the 
length of stroke expressed in feet multiplied by the 
number of revolutions per minute. 



194 ENGINEERING 

R. P. M. Revolutions per minute. 

Net horse power. I. H. P. minus the friction of the 
engine. 

Compression, The action of the piston as it nears the 
end of the stroke, in reducing the volume and raising 
the pressure of the steam retained in the cylinder 
ahead of the piston by the closing of the exhaust 
valve. 

Boyle^s or Mariotte' s law of expanding gases, **The 
pressure of a gas at a constant temperature varies 
inversely as the space it occupies." Thus, if a given 
volume of gas is confined at a pressure of 50 lbs. per 
square inch and it is allowed to expand to twice its 
volume, the pressure will fall to 25 lbs. per square inch. 

Adiabatic curve, A curve representing the expansion 
of a gas which loses no heat while expanding. Some- 
times called the curve of no transmission. 

Isothermal curve, A curve representing the expan- 
sion of a gas having a constant temperature but 
partially influenced by moisture, causing a variation in 
pressure according to the degree of moisture or satura- 
tion. It is also called the theoretical expansion 
curve. 

Expansion curve. The curve traced upon the dia- 
gram by the indicator pencil showing the actual 
expansion of the steam in the cylinder. 

First law of ther?nodynamics. Heat and mechanic il 
energy are mutually convertible. 

Power, The rate of doing work, or the number of 
foot pounds exerted in a given time. 

Unit of work. The foot pound, or the raising of one 
pound weight one foot high. 

First law of motion. All bodies continue either in a 
state of rest or of uniform motion in a straight line, 



DEFINITIONS AND TABLES 195 

except in so far as they may be compelled by 
impressed forces to change that state. 

Work, Mechanical force or pressure cannot be con- 
sidered as work unless it is exerted upon a body and 
causes that body to move through space. The product 
of the pressure multiplied by the distance passed 
through and the time thus occupied is work. 

Momentum, Force possessed by bodies in motion, 
or the product of mass and density. 

Dynamics, The science of moving powers or of 
matter in motion, or of the motion of bodies that 
mutually act upon each other. 

Force,, That which alters the motion of a body, or 
puts in motion a body that was at rest. 

Maxmum. theoretical duty of steam, is the product of 
the mechanical equivalent of heat, viz., 778 ft. lbs. 
multiplied by the total heat units in a pound of steam. 
Thus, in one pound of steam at 212° reckoned from 32° 
the total heat equals 1,146.6 heat units. Then 
778 X 1,146.6 equals 892,054.8 ft. lbs. = maximum duty. 

Steam efficiency may be expressed as follows: 

Heat converted into useful work , . ^^ 

■ Y^ — 7 -j-^ and maximum effic- 

Heat expended 

iency can only be attained by using steam at 

as high an initial pressure as is consistent with safety 

and at as large a ratio of expansion as possible. The 

percentage of efificiency of steam used at atmospheric 

pressure in a non-expansive engine is very low; as, for 

instance, the heat expended in the evaporation of one 

pound of water at 32° into steam at atmospheric 

pressure = 1,146.6 heat units, and the volume of steam 

so generated = 26.36 cu. ft. 

One cubic foot of steam at 212° contains energy 

equal to 144x14.7 = 2,116.8 ft. lbs., and 26.36 cu. 



196 ENGINEERING 

ft. = 2, 1x6.8 X 26.36= 55,798.84 ft. lbs., which divided by 
the mechanical equivalent of heat, viz., 778 ft. 
lbs. = 71.72 heat units, available for useful work. The 
per cent, of efficiency therefore is '^^'^\^q f^ = 6.28 per 
cent. But suppose the initial pressure to have been 
200 lbs. absolute, and that the steam is allowed to 
expand to thirty times its original volume. The heat 
expended in evaporating a pound of water at 32° into 
steam at 200 lbs. absolute pressure = 1,198.3 heat units, 
and the volume of steam so generated = 2.27 cu. ft. 
The average pressure during expansion would be 29.34 
IbSo per square inch and the volume when expanded 
thirty times would equal 2,2y x 30 = 68. i cu. ft. 

One cubic foot of steam at 29.34 lbs. pressure equals 
144 X 29.34 = 4,224.96 ft. lbs., and 68.1 cu. ft. will equal 
4224.96x68.1 = 287,719.7 ft. lbs. of energy, which 
divided by the equivalent, 778, equals 370.2 heat units, 
and the per cent, of efficiency will be ^'^I'l^l^ = 30.8 
per cent. 

Engine efficiency. If the engine is considered merely 
as a machine for converting into useful work the heat 
energy in the steam regardless of the cost of fuel, its 
efficiency may be expressed as follows: 
Heat converted into useful work 
Total heat received in the steam 

Example, Assume an engine to be receiving steam 
at 95 lbs. absolute pressure, that the consumption of 
dry steam per horse power per hour equals 20 lbs., that 
the friction of the engine amounts to 15 per cent., and 
that the temperature of the feed water is raised from 
60° to 170° by utilizing a portion of the exhaust. 

In a pound of steam at 95 !bs. absolute there are 
1,180.7 beat units, and in a pound of water at 170° there 



DEFINITIONS AND TABLES 197 

are J38.6 units of heat, but 28.01 of these heat units 
were in the water at its initial temperature of 60°. 
Therefore the total heat added to the water by the 
exhaust steam equals 138.6 — 28.01 = no. 59 heat units, 
and the total heat in each pound of steam to be 
charged up to the engine is 1,180.7 - 1 10. 59 = 1,070. 11, 
and the total for each horse power developed per hour 
will be 1,070.11 X 20 = 21,402.2 heat units. 

A horse power equals 33,000 ft. lbs. per minute, or 
sixty times 33,000= 1,980,000 ft. lbs. per hour. From 
this must be deducted 15 per cent, for friction of the 
engine, leaving 1,683,000 ft. lbs. for useful work. 
Dividing this by the equivalent, viz., 778 ft. lbs., 
gives 2,163.2 heat units as the heat converted into one 
horse power of work in one hour, and the percentage 
of efficiency of the engine will be ^'^lf^l^2^ = 10. i per 
cent. 

Efficiency of the plant as a zvhole includes boiler and 
engine efficiency and is to be figured upon the basis of 
Heat converted into useful work 
Calorific or heat value of fuel 

Horse power constant oi an engine is found by multi- 
plying the area of the piston in square inches by the 
speed of the piston in feet per minute and dividing the 
product by 33,000. It is the power the engine would 
develop with one pound mean effective pressure. To 
find the horse power of the engine, multiply the M. 
E, P. of the diagram by this constant. 

Logarithms, A series of numbers 'having a certain 
relation to the series of natural numbers, by means of 
which many arithmetical operations are made com- 
paratively easy. The nature of the relation will be 
understood by considering two simple series, such as 
the following, one proceeding from unity in geomet- 



198 ENGINEERING 

rical progression and the other from o in arithmetical 
progression: 

Geom. series, i, 2, 4, 8, 16, 32, 64, 128, 256, 512, etc. 

Arith. series, o, i, 2, 3, 4, 5, 6, 7, 8, 9, etc. 

Here the ratio of the geometrical series is 2 and any 
term in the arithmetical series expresses how often 2 
has been multiplied into i to produce the correspond- 
ing term of the geometrical series. Thus, in proceeding 
from I to 32 there have been 5 steps or multiplications 
by the ratio 2; in other words, the ratio of 32 to i is 
compounded 5 times of the ratio of 2 to i. The above 
is the basic principle upon which common logarithms 
are computed. 

Hyperbolic logarithms. Used in figuring the M. E. P. 
of a diagram from the ratio of expansion and the 
initial pressure. Thus, hyperbolic logarithm of ratio 
of expansion 4- i multiplied by absolute initial pres- 
sure and divided by ratio of expansion = mean forward 
pressure. From this deduct total back pressure and 
the remainder will be mean effective pressure. The 
hyperbolic logarithm is found by multiplying the com- 
mon logarithm by the constant 2.302585. Table 8 
gives the hyperbolic logarithms of numbers usually 
required in calculations of the above nature. 

Steam cofisumption per horse power per hour. The 
weight in pounds of steam exhausted into the atmos- 
phere or into the condenser in one hour divided by the 
horse power developed. It is determined from the 
diagram by selecting a point in the expansion curve 
just previous to the opening of the exhaust valve and 
measuring the absolute pressure at that point. Then 
the piston displacement up to the point selected, plus 
the clearance space, expressed in cubic feet, will give 
the volume of steam in the cylinder, which multiplied 



DEFINITIONS AND TABLES 



199 



Table 8. 

Hyperbolic Logarithms. 



No. 


Log. 


No. 


Log. 


No. 


Log. 


No. 


Log. 


No. 


Log. 


I.OI 


. 0099 


3.00 


1.0986 


5.00 


I . 6094 


7.00 


1.9459 


9.00 


2.1972 


1,05 


0.0487 


3.05 


I.1151 


5.05 


1 .6194 


7.05 


1.9530 


9.05 


2.2028 


1. 10 


0.0953 


3.10 


I.1341 


5.10 


1.6292 


7.10 


1.9600 


9. 10 


2 . 2083 


1. 15 


0.1397 


3.15 


I. 1474 


5.15 


I . 6390 


7.15 


I. 9671 


9.15 


2.2137 


1.20 


0.1823 


3.20 


1.1631 


5.20 


1.6486 


7.20 


1.9740 


9.20 


2.2192 


1.25 


0.2231 


3.25 


I. 1786 


5.25 


1.6582 


7.25 


1.9810 


9.25 


2 . 2246 


1.30 


0.2623 


3.30 


I. 1939 


5.30 


1.6677 


7.30 


1.9879 


9.30 


2.2310 


1.35 


. 3001 


3.35 


I . 2090 


5.35 


I. 6771 


7.35 


1.9947 


9.35 


2.2354 


1.40 


0.3364 


3.40 


I .2238 


5.40 


I . 6864 


7.40 


2.0015 


9.40 


2 . 2407 


1.45 


0.3715 


3.45 


1.2384 


5.45 


1.6956 


7.45 


2 . 001 8 


9.45 


2.2460 


1.50 


0.4054 


3.50 


1.2527 


5.50 


1.7047 


7.50 


2.0149 


9.50 


2.2513 


1.55 


0.4382 


3.55 


1.2669 


5.55 


I. 7138 


7.55 


2.0215 


9.55 


2.2565 


1.60 


0.4700 


3.60 


1.2809 


5.60 


1.7228 


7.60 


2.0281 


9.60 


2.2618 


1.65 


0.5007 


3.65 


I . 2947 


5.65 


I. 7316 


7.65 


2.0347 


9.65 


2 . 2670 


1.70 


0.5306 


3.70 


1.3083 


5.70 


I . 7405 


7.70 


2.0412 


9.70 


2.2721 


1.75 


0.5596 


3.75 


I. 3217 


5.75 


I. 7491 


7.75 


2.0477 


9.75 


2.2773 


1.80 


0.5877 


3.80 


1.3350 


5.80 


1.7578 


7.80 


2.0541 


9.80 


2.2824 


1.85 


0.6151 


3.85 


1.3480 


5.85 


1.7664 


7.85 


2 . 0605 


9.85 


2.2875 


1.90 


0.6418 


3.90 


I. 3610 


5.90 


1.7750 


7.90 


2.0668 


9.90 


2.2925 


1.95 


0.6678 


3.95 


1.3737 


5.95 


1.7834 


7.95 


2.0731 


9-95 


2.2976 


2.00 


0.6931 


4.00 


1.3863 


6.00 


1. 7918 


8.00 


2.0794 


10.00 


2.3026 


2.05 


0.7178 


4.05 


1.3987 


6.05 


I . 8000 


8.05 


2.0857 


10.25 


2.3273 


2.10 


0.7419 


4.10 


I. 4010 


6.10 


I . 8083 


8.10 


2.0918 


10.50 


2.3514 


2.15 


0.7654 


4.15 


I. 4231 


6.15 


I. 8164 


8.15 


2.0988 


10.75 


2.3749 


2.20 


0.7885 


4.20 


I. 4351 


6.20 


1.8245 


8.20 


2.1041 


11.00 


2.3979 


2.25 


o.8rio 


4.25 


1 . 4469 


6.25 


1.8326 


8.25 


2.1102 


12.00 


2.4849 


2.30 


0.8329 


4.30 


1.4586 


6.30 


I . 8405 


8.30 


2.1162 


13.00 


2.5626 


2.35 


0.8544 


4.35 


I. 4701 


6.35 


1.8484 


8.35 


2.1222 


14.00 


2.6390 


2.40 


0.8755 


4.40 


I. 4816 


6.40 


1.8563 


8.40 


2.1282 


15.00 


2.7103 


2.45 


0.8961 


4.45 


1.4929 


6.45 


I . 8640 


8.45 


2.1342 


16.00 


2.7751 


2.50 


0.9163 


4.50 


I . 5040 


6.50 


I. 8718 


8.50 


2 . 1400 


17.00 


2.8332 


2.55 


0.9361 


4.55 


1.5151 


6.55 


1.8795 


8.55 


2.1459 


18.00 


2 . 8903 


2.60 


0.9555 


4.60 


1.5260 


6.60 


1.8870 


8.60 


2.1518 


19.00 


2.9444 


2.65 


0.9746 


4.65 


1.5369 


6.65 


1.8946 


8.65 


2.1576 


20.00 


2.9957 


2.70 


0.9932 


4.70 


1.5475 


6.70 


1. 902 1 


8.70 


2.1633 


21.00 


3.0445 


2.75 


1.0116 


4.75 


1.5581 


6.75 


1.9095 


8.75 


2.1690 


22.00 


3.0910 


2.80 


1.0296 


4.80 


1.5686 


6.80 


I. 9169 


8.80 


2.1747 


23.00 


3.0355 


2.85 


1.0473 


4.85 


1.5790 


6.85 


1.9242 


8.85 


2. 1804 


24.00 


3.1780 


2.90 


I .0647 


4.90 


1.5892 


6.90 


I. 9315 


8. go 


2.1860 


25 .00 


3.2189 


2.95 


I. 0818 


4.95 


1.5994 6.95| 


1.9387 


8.95 


2.1916 


30.00 


3.3782 



£00 ENGINEERING 

by the weight per cubic foot of steam at the pressure 
as measured will give the weight of steam consumed 
during one stroke. From this should be deducted the 
steam saved by compression as shown by the diagram, 
in order to get a true measure of the economy of the 
engine. Having thus determined the weight of steam 
consumed for one stroke, multiply it by twice the num- 
ber of strokes per minute and by 60, which will give 
the total weight consumed per hour. This divided by 
the horse power will give the rate per horse power per 
hour. 

Cylinder condensation and reevaporation. When the 
exhaust valve opens to permit the exit of the steam 
there is a perceptible cooling of the walls of the 
cylinder, especially in condensing engines when a high 
vacuum is maintained. This results in more or less 
condensation of the live steam admitted by the open- 
ing of the steam valve; but if the exhaust valve is 
caused to close at the proper time so as to retain a 
portion of the steam to be compressed by the piston on 
the return stroke, a considerable portion of the water 
caused by condensation will be reevaporated into steam 
by the heat and consequent rise in pressure caused by 
compression. 

Ordinates, Parallel lines drawn at equal distances 
apart across the face of the diagram, and perpendic- 
ular to the atmospheric line. They serve as a guide to 
facilitate the measurement of the average forward 
pressure throughout the stroke, or the pressure at any 
point of the stroke if desired. 

Eccentric, A mechanical device used in place of a 
crank for converting rotary into reciprocating motion. 
An eccentric is in fact a form of crank in which the 
crank pin, corresponding to the eccentric sheave, 



DEFINITIONS AND TABLES 201 

i 

embraces the shaft, but owing to the great leverage at 

which the friction between the sheave and the strap 
acts, compared with its short turning leverage, it can 
only be used to advantage for the purpose named 
above. 

Eccentric throw is the distance from the center of the 
eccentric to the center of the shaft. This definition 
also applies to the term "radius of eccentricity.*' 

Eccentric position. The location of the highest point 
of the eccentric relative to the center of the crank pin, 
measured or expressed in degrees. 

Angular advance . The distance that the high point 
of the eccentric is set ahead of a line at right angles 
with the crank. In other words, the lap angle plus 
the lead angle. If a valve had neither lap nor lead, 
the position of the high point of the eccentric would 
be on a line at right angles with the crank; as for 
instance, the crank being at o° the eccentric would 
stand at 90°. 

Valve travel. The distance covered by the valve in 
its movement. It equals twice the throw of the eccen- 
tric. This refers to engines having a fixed cut off. In 
the case of an engine with a variable automatic cut off 
the travel of the cut off valve is regulated by the gov- 
ernor. 

Lap, The amount that the ends of the valve project 
over the edges of the ports when the valve is at mid 
travel. 

Outside or steam lap. The amount that the end of 
the valve overlaps or projects over the outside edge of 
the steam port. 

Inside lap. The lap of the inside or exhaust edge of 
the valve over the inside edge of the port. 

Lead. The amount that the port is open when the 



202 ENGINEERING 

crank is on the dead center. The object of giving a 
valve lead is to supply a cushion of live steam which, 
in conjunction with that already confined in the clear- 
ance space by compression, shall serve to bring the 
moving parts of the engine to rest quietly at the end 
of the stroke, and also quicken the action of the piston 
in beginning the return stroke. 

Compression, Closing of the exhaust passage before 
the steam is entirely exhausted from the cylinder. 
A certain quantity of steam is thus compressed into 
the clearance space. 

Throttling governor. Used to regulate the speed of 
engines having a fixed cut off. The governor controls 
the position of a valve in the steam pipe, opening or 
closing it according as the engine needs more or less 
steam in order to maintain a regular speed. 

Automatic or variable cut off. In engines of this type 
the full boiler pressure is constantly in the valve chest 
and the speed of the engine is regulated by the gov- 
ernor controlling the point of cut off, causing it to take 
place earlier or later according as the load on the 
engine is lighter or heavier. 

Fixed cut off. This term is applied to engines in 
which the point of cut off remains the same regardless 
of the load, the speed being regulated by a throttling 
governor as explained above. 

Isochronal or shaft governor. This device in which 
the centrifugal and centripetal forces are utilized, as 
in the fly ball governor, is generally applied to auto- 
matic cut off engines having reciprocating or slide 
valves. It is attached to the crank shaft and its func- 
tion is to change the position of the eccentric, which 
is free to move across the shaft within certain pre- 
scribed limits, but is at the same time attached to the 



ENGINEERING 



203 



Table 9. 
Areas and Circumferences of Circles. 



Diam. 


Area. 


Circum.' 


Diam. 


Area. 


Circum. 


Diam. 


Area. 


Circum. 


.25 


.049 


.7854 


15.5 


188.692 


48.694 


31 


754.769 


97.389 


.5 


.1963 


1.5708 


16 


201.062 


50.265 


31.25 


766.992 


98.175 


I.O 


.7854 


3.1416 


16.25 


207.394 


51.051 


31.5 


799.313 


98.908 


1.25 


J. 2271 


3.9270 


16.5 


213.825 


51.836 


32 


804.249 


100.53 


1.5 


I.7671 


4.7124 


17 


226.980 


53.407 


32.25 


816.86 


IOI.31 


2 


3.1416 


6.2832 


17.25 


233.705 


54.192 


33 


855.30 


103.67 


2.25 


3.9760 


7.0686 


17.5 


240.520 


54.978 


33.25 


868.30 


104.45 


2.5 


4.9087 


7.8540 


18 


254.469 


56.548 


33.5 


881.41 


105.24 


3 


7.0686 


g.4248 


18.25 


261.587 


57.334 


34 


907.92 


106.81 


3.25 


8.2957 


10.210 


18.5 


268.803 


58.119 


34.25 


921.32 


107.60 


3-5 


9. 62 1 1 


10.995 


19 


283.529 


59.690 


34.5 


934.82 


108.38 


4 


12.566 


12.566 


19.25 


291.039 


60.475 


35 


962.11 


106.95 


4.25 


14.186 


13.351 


19.5 


298.648 


61.261 


35.25 


975.90 


110.74 


4.5 


15.904 


14.137 


20 


314.160 


62.832 


35.5 


989.80 


III. 52 


5 


19-635 


15.708 


20.25 


322.063 


63.617 


36 


1017.8 


113.09 


5.25 


21.647 


16.493 


20.5 


330.064 


64.402 


36.25 


1032.06 


113.88 


5.5 


23.758 


17.278 


21 


346.361 


65.973 


36.5 


1046.35 


114.66 


6 


28.274 


18.849 


21.25 


354.657 


66.759 


37 


1075.21 


116.23 


6.25 


30.679 


19.635 


21.5 


363.051 


67.544 


37.25 


1089.79 


II7.OI 


6.5 


33.183 


20.420 


22 


380.133 


69.115 


37.5 


1104.46 


I17.81 


7 


38.484 


21.991 


22.25 


388.822 


69.900 


38 


1 134. 1 1 


119.38 


7.25 


41.282 


22.776 


22.5 


397.608 


70.686 


38.25 


1149.08 


120.16 


7.5 


44.178 


23.562 


23 


415.476 


72.256 


38.5 


I164.15 


120.95 


8 


50.265 


25.132 


23.25 


424.557 


73.042 


39 


1194.59 


122.52 


8.25 


53.456 


25.918 


23.5 


433.731 


73.827 


39.25 


1209.95 


123.30 


8.5 


56.745 


26.703 


24 


452.390 


75.398 


39.5 


1225.42 


124.OQ 


9 


63.617 


28.274 


24.25 


461.86^ 
471.436 


76.183 


40 


1256.64 


125.66 


9.25 


67.200 


29.059 


24.5 


76.969 


40.25 


1272.39 


126.44 


9-5 


70.882 


29.845 


25 


490.875 


78.540 


40.5 


1288.25 


127.23 


10 


78 54O 


31.416 


25.25 


500.741 


79.325 


41 


1320.25 


128.80 


10,25 


82.516 


32.201 


25.5 


510.706 


80.110 


41.25 


1336.40 


129.59 


10.5 


86.590 


32.986 


26 


530.930 


81.681 


41.5 


1352.65 


130.37 


II 


95.033 


34.557 


26.25 


541.189 


82.467 


42 


1385.44 


131.94 


11.25 


99.402 


35.343 


26.5 


551.547 


83.252 


42,25 


1401.98 


132.73 


II. 5 


103.869 


36.128 


27 


572.556 


84.823 


42.5 


1418.62 


133.51 


12 


113.097 


37.699 


27.25 


583.208 


85.608 


43 


1452.20 


135.08 


12.25 


117.859 


38.484 


27.5 


593.958 


86.394 


43.25 


1469.13 


135.87 


12.5 


122.718 


39.270 


28 


615.753 


87.964 


43.5 


1486.17 


136.65 


13 


132.732 


40. 840 


28.25 


626.798 


88.750 


44 


1520.53 


138.23 


13.25 


137.886 


41.626 


28.5 


637.941 


89.535 


44.25 


1537.86 


139.01 


13.5 


143.130 


42.411 


29 


660.521 


91.106 


44.5 


1555.28 


139.80 


14 


153.938 


43.982 


29.25 


671.958 


91.891 


45 


1590.43 


141.37 


14.25 


159.485 


44- 767 


29.5 


683.494 


92.677 


45.25 


1608.15 


142.15 


14.5 


165.130 


45.553 


30 


706.860 


94.248 


45.5 


1625.97 


142.94 


15 


176.715 


47.124 


30.25 


718.690 


95.033 


46 


1661.90 


144.51 


15.25 


182.654 


47.909 


30.5 


730.618 


95.818 


46.2? 


1680.01 


145.29 



204 



DEFINITIONS AND TABLES 



Table 9 — Co?iti7iued. 



Diam. 


Area. 


Circum. 


Diam. 


Area. 


Circum. 


Diam. 


Area. 


Circum. 


46.5 


i6g8.23 


146.08 


62.25 


3043.47 


195.56 


78 


4778.37 


245.04 


47 


1734.94 


147.65 


62.5 


3067.96 


196.35 


78.25 


4809.05 


245.83 


47.25 


1753.45 


148.44 


63 


3117.25 


197.92 


78.5 


4839.83 


246.61 


47.5 


1772.05 


149.22 


63.25 


3142.04 


198.71 


79 


4901.68 


248.19 


48 


1809.56 


150.79 


63.5 


3166.92 


199.50 


79.25 


4932.75 


248.97 


48.25 


1828.46 


151.58 


64 


3216.99 


201.06 


79-5 


4963.92 


249. 76 


48.5 


1847.45 


152.36 


64.25 


3242.17 


201.85 


80 


5026.56 


251.33 


49 


1885.74 


153.93 


64.5 


3267.46 


202.68 


80.5 


5089.58 


252.90 


49.25 


1905.03 


154.72 


65 


3318.31 


204.20 


81 


5153.00 


254.47 


49-5 


1924.42 


155.50 


65.25 


3343.88 


204.99 


81.5 


5216.82 


256.04 


50 


1963.50 


157.08 


65.5 


3369.56 


205.77 


82 


5281.02 


257.61 


50.25 


1983.18 


157.86 


66 


3421.20 


207.34 


82.5 


5345.62 


259.18 


50.5 


2002.96 


158.65 


66.25 


3447.16 


208.13 


83 


5410.62 


260.75 


51 


2042.82 


160.22 


66.5 


3473.23 


208.91 


83.5 


5476.00 


262.32 


51.25 


2062.90 


161.00 


67 


3525.66 


210.49 


84 


5541.78 


263.89 


51.5 


2083.07 


161.79 


67.25 


3552.01 


211.27 


84.5 


5607.95 


265.46 


52 


2123.72 


163.36 


67.5 


3578.47 


212.06 


85 


5674.51 


267.04 


52.25 


2144.19 


164.14 


68 


3631.68 


213.63 


85.5 


5741-47 


268.60 


52.5 


2164.75 


164.19 


68.25 


3658.44 


214.41 


86 


5808.81 


270.17 


53 


2206.18 


166.50 


68.5 


3685.29 


215.20 


86.5 


5876.55 


271.75 


53.25 


2227.05 


167.29 


69 


3739.28 


216,77 


87 


5944.66 


273.32 


53.5 


2248.01 


168.07 


69.25 


3766.43 


217.55 


87.5 


6013.21 


274.89 


54 


2290.22 


169.64 


69.5 


3793.67 


218.34 


88 


6082.13 


276.46 


54.25 


2311.48 


170.43 


70 


3848.46 


219.91 


88,5 


6151.44 


278.03 


54.5 


2332.83 


171. 21 


70.25 


3875.99 


220.70 


89 


6221.15 


279.60 


55 


2375.83 


172.78 


70.5 


3903.63 


221.48 


89.5 


6291.25 


281.17 


55.25 


2397.48 


173.57 


71 


3959.20 


223.05 


90 


6371.64 


282.74 


55.5 


2419.22 


174.35 


71.25 


3987.13 


223.84 


90.5 


6432.62 


284.31 


56 


2463.01 


175.92 


71.5 


4015.16 


224.62 


91 


6503.89 


285.88 


56.25 


2485.05 


176.71 


72 


4071.51 


226.19 


91.5 


6573.56 


287.46 


56.5 


2507.19 


177.5 


72.25 


4099.83 


226.98 


92 


6647.62 


289.03 


57 


2551.76 


179.07 


72.5 


4128.25 


227.75 


92.5 


6720.07 


290.60 


57.25 


2574.19 


179.85 


73 


4185.39 


229.34 


93 


6792.92 


292.17 


57.5 


2596.72 


;i8o.64 


73.25 


4214. II 


230.12 


93.5 


6866.16 


293.74 


58 


2642.08 


182.21 


73-5 


4242.92 


230.91 


94 


6939.79 


295.31 


58.25 


2664.91 


182.99 


74 


4300.85 


232.48 


94.5 


7013.81 


296.88 


58.5 


2687.83 


183.78 


74-25 


4329.95 


233.26 


95 


7088.23 


298.45 


59 


2733.97 


185.35 


74.5 


4359.16 


234.05 


95.5 


7163.04 


300.02 


59.25 


2757.19 


186.14 


75 


4417.87 


235.62 


96 


7238.25 


301.59 


59.5 


2780.51 


186.92 


75.25 


4447.37 


236.40 


96.5 


7313-80 


303.16 


60 


2827.44 


188.49 


75.5 


4476.97 


237.19 


97 


7389.81 


304.73 


60.25 


2851.05 


189.28 


76 


4536.37 


238.76 


97-5 


7466.22 


306.30 


60.5 


2874.76 


190.06 


176.25 


4566.36 


239-55 


98 


7542.89 


307.88 


6i 


2922.47 


191.64 


76.5 


4596.35 


240.33 


98.5 


7620.09 


309.44 


61.25 


2946.47 


192.42 


77 


4656.63 


241.90 


99 


7697.70 


311.02 


61.5 


2970.57 


193.21 


77 25 


4686.92 


242.69 


99.5 


7775.63 


312.58 


62 


3019.07 


194. 78 


77.5 


4717.30 


243.47 


100 


7854.00 


314.16 



DEFINITIONS AND TABLES 205 

governor. The angular advance of the eccentric is 
thus increased or diminished, in fact is entirely under 
the control of the governor, and cut off occurs earlier 
or later according to the demands of the load on the 
engine. 

Adjustable cut off. One in which the point of cut off 
may be regulated or adjusted by hand by means of a 
hand wheel and screw attached to the valve stem, the 
supply of steam being regulated by a throttling gov- 
ernor. 

Questions 

1. What is absolute pressure? 

2. What is gauge pressure? 

3. What is initial pressure? 

4. What is terminal pressure and how may it be 
ascertained theoretically? 

5. What is back pressure? 

6. What is absolute back pressure? 

7. What is meant by ratio of expansion? 

8. What does the term wire drawing mean when 
applied to an indicator diagram? 

9. What is condensor pressure? 

ID. What does the term vacuum imply? 

11. What is absolute zero? 

12. What is meant by the term piston displacement? 

13. What is piston clearance? 

14. What is steam clearance? 

15. What is a horsepower? 

16. What is meant by piston speed? 

17. Define Boyle's law of expanding gases. 

18. What is an adiabatic curve? 

19. What is an isothermal curve? 

20. What is the first law of thermodynamics? 

21. What is the unit of work? 



206 



ENGINEERING 



22. Define the first law of motion. 

23. What is momentum? 

24. What is the maximum theoretical duty of steam? 

25. What is meant by the term steam efficiency? 

26. How may the term engine efficiency be defined? 

27. What is meant by the term efficiency of the 
plant, and how may it be ascertained? 

28. How is the horse power constant of an engin- 
found, and what does it mean? 

29. What are common logarithms? 

30. What are hyperbolic logarithms, and how sikt 
they found? 

31. What are ordinates as applied to an indicator 
diagram? 

32. What 

33. What 

34. What 

35. What 

36. What 

37. What 

38. What 

39. What 

40. What 

41. What 

42. What 

43. What 

44. What 

45. What 



s an eccentric? 

s meant by the throw of an eccentric? 

s meant by position of the eccentric? 

s angular advance? 

s valve travel? 

s lap? 

s inside lap? 

s outside lap? 

s lead? 

s a throttling governor? 

s meant by the term fixed cut off? 

s meant by an automatic cut off? 

s an isochronal governor? 

s an adjustable cut off? 



CHAPTER IX 

DIAGRAM ANALYSIS 

Diagram analysis — Figure illustrating the various points in an 
indicator diagram — Disadvantage of unequal cut off — Dia- 
gram from compound condensing engine — Rules for finding 
M. E. P. when the initial and terminal pressures are known, 
and the ratio of expansion — Equalizing the work done in the 
high and low pressure cylinders — Misleading diagrams caused 
by dirt in indicator cylinder — Diagrams showing effect of 
cramped exhaust — Table of factors for calculating the steam 
consumption from the terminal pressure. 

In the following study of indicator diagrams all the 
illustrations are reproductions of actual diagrams taken 
under ordinary working conditions. Figs. 50 and 51 
are here introduced in order to define the different 




FIGURE 50. 

points, lines and curves. Fig. 5C was taken from a 
large vertical engine with the corliss valve motion. 

The engine being of slow speed and extremely long 
stroke (10 ft.) with a clearance of but I per cent., the 
compression beginning at C and ending at B is some- 
what lighter than is ordinarily given to shorter stroke 

207 



208 ENGINEERING 

engines. From B to D is the admission line, which 
being practically perpendicular to the atmospheric 
line A, shows sufficient lead and ample port area. 
From D to E is the steam line. Cut off occurs at E, 
and from E to F is the expansion curve. At F the 
point of release is quite sharply defined, as it should 
be. From F to G is the exhaust line, and from G to C 
the line of back pressure, sometimes called the line of 
counter pressure for the reason that the pressure indi- 
cated by it acts counter or in opposition to the forward 
pressure of the steam on the piston. This engine is a 




FIGURE 51. 

simple condensing engine and the nearness of the 
back pressure line to the line of perfect vacuum V 
shows that an excellent vacuum was maintained in the 
condenser. 

Fig. 51 is from a Buckeye automatic cut off engine 
having a shaft governor and what is termed a riding 
cut off, that is the cut off valve slides to and fro on 
the back of the main valve. The engine is horizontal 
non-condensing, the cylinder being 28 in. bore by 56 
in. stroke, and, at the time the diagram was taken, 



DIAGRAM ANALYSIS 209 

developed 357. 58 horse power with a piston speed of 
728 ft. per minute. The steam consumption per I. H. 
P. per hour was 26 lbs., a rather high rate, but this was 
owing to the fact that the engine was located too far 
from the boilers, and as there were a large number of 
elbows in the steam pipe the pressure was greatly 
reduced at the engine. Thus wire drawing of the 
steam was caused, which is plainly indicated by the 
downward inclination of the steam line, D E. 

In a well proportioned engine having a steam pipe 
of sufficiently large area, the steam line should paral- 
lel the atmospheric line up to the point of cut off. 
Fig. 51 indicates proper release of the steam at F, and 
the back pressure from G to C, which is 3 lbs. above 
the atmospheric line, shows a reasonably free passage 
of the exhaust steam. 

Figs. 52 to 57 illustrate diagrams from three new 
vertical corliss engines supplying power for an electric 
lighting plant, which the author was requested to test 
and adjust after they had been in operation a few 
months. The valves had previously been set by the 
erecting engineer at the time the engines were set up. 
Each one of these engines exhausted into a separate 
condenser of the Jet type, into which the condensing 
water was forced under pressure and from which the 
overflow was discharged by gravity into a sewer. 
There was no air pump and as a consequence the 
vacuum maintained was very low, usually from 10 to 
15 in., and at times still less, so that the beneficial 
results of condensing were only partially realized. 

For convenience the diagrams from each engine will 
be treated in numerical order, beginning with engine 
No. I. This engine was 24 x 48 in., running 70 R. P. 
M., with a boiler pressure of 68 lbs. A 40 spring was 



210 



ENGINEERING 



used in the indicator. The principal defect was the 
lack of sufficient lead on both ends, as indicated by 
the inclination inward of the admission lines and the 
rounded corners of the steam lines at the beginning of 




FIGURE 52. 

the stroke. (See Fig. 52.) There was also more com- 
pression, especially on the bottom end, than was neces- 
sary, considering the size of the engine and the speed. 
The necessary changes having been made, the indi- 
cator was again applied and the diagram Fig. 53 was 




FIGURE 53. 



obtained, which shows the distribution of the steam to 
be satisfactory, although at the time of taking this 
diagram the boiler pressure was only 60 lbs., while it 
should have been 68 or 70 lbs., because with the latter 



DIAGRAM ANALYSIS 211 

pressure still better results could have been attained. 
The I. H. P. was 235 and the steam used per I. H. P. 
per hour was 18 lbs. 

Fig. 54 is the original diagram from engine No. 2, 




FIGURE 54. 

and shows bad valve adjustment all around, with the 
exception of lead on the top end. The variation in 
the points of cut off is the worst feature; cut off 
taking place on the bottom at 29 per cent, of the 
stroke, while on the top end it does not occur until 



-4 



FIGURE 55. 



the piston has traveled through 42 per cent, of the 
stroke. There is more compression also than is 
needed. This engine was 18 x 42 in., running at a 
speed of 78 R. P. M., and the steam consumption, 



212 



ENGINEERING 



according to diagram Fig. 54, was 33 lbs. per I. H. P. 
per hour. Having equalized the cut off and reduced 
the compression by making the necessary changes in 
the valve gear, the indicator was again applied, result- 
ing in diagram Fig. 55, which maybe considered prac- 




FIGURE 56. 



tically perfect. The boiler pressure was 68 lbs. and 
the spring used was a No. 40. The steam consump- 
tion was reduced to 22 lbs. per I. H. P. per hour as 
compared to 33 lbs. in Fig. 54. 

Figs. 56 and 57 represent diagrams from engine No. 
3, which was the same size as No. i, viz., 24x48 in., 




FIGURE 5 



and running at 72 R. P. M. The original diagram, 
Fig. 56, shows too little lead on both ends, but espe- 
cially on the top. There is also lack of compression 
on the bottom end. The boiler pressure was 60 lbs. 
and the scale of spring 40. Fig. 57, taken after the 



DIAGRAM ANALYSIS 



213 



necessary adjustments had been made, shows much 
better valve performance. The horse power developed 
was 251 and the steam consumption was 20.5 lbs. per 
I. H. P. per hour. The rather high rate of steam 
consumption for this engine as compared with engine 
No. I, which was the same size but consumed only 18 
lbs. of steam per I. H. P. per hour, was due to two 
causes. First, a low vacuum; second, low initial pres- 
sure necessitating a late cut off. 

Figs, 58 to 61, inclusive, are diagrams from a Bullock 
horizontal non-condensing corliss engine which had 




FIGURE 58. 



been running about eight or nine months when it fell 
to the author's lot to apply the indicator to the engine, 
not only for the purpose of adjusting the valve motion, 
but also to make a series of tests for the purpose of 
ascertaining the amount of power delivered by the 
engine to each one of several different departments 
which were receiving power from this source. 

The dimensions of the engine were as follows: bore 
of cylinder, 32 in.; stroke, 5 ft. At the time Fig. 58 
was taken the engine was making 62 R. P. M. and the 
boiler pressure was only 50 lbs. A 30 spring was 
used. Although the load on the engine was very light 



214 



ENGINEERING 



at the time, yet the diagram served as a guide to some 
extent in setting the valves, and by taking off the bon- 
nets from the valve chests and making the necessary 
changes in the adjustment by the marks on the valves 




FIGURE 59. 

a pretty fair job was made of it, as will be seen by 
referring to Fig. 59. The reducing motion was a 
pantograph, described in Chapter VIII, and as it is 
very easy to vary the travel of the paper drum with 
this motion, diagrams of different lengths were taken 
until the one which appeared to be the most satisfac- 




FIGURE 60. 



tory was obtained. The slight hump in the expansion 
curve immediately after cut off was probably caused 
by a speck of dirt or grit which momentarily checked 
the indicator piston on the down stroke. The com- 



DIAGRAM ANALYSIS 



215 



pression on the crank end 's not sufficient and the 
exhaust valve rod on that end was slightly lengthened, 
resulting in the production of diagram Fig. 60. In 
this diagram the familiar hump in the crank end expan- 
sion curve reappears, but in a different location, being 
nearer the end of the stroke. It will also be noticed 
that the length of Fig. 60 has been considerably- 
reduced from that of Figs. 58 and 59, it being about 
one inch shorter. 



Msfid 




FIGURE 61. 



The boiler pressure and the load on this engine were 
gradually increased from time to time, from 50 lbs. 
and a light load, (as shown by Fig. 58) to 60 lbs. and 
335 horse power, (as indicated by Fig. 59 taken some 
three months later) and when Fig. 61 was taken, about 
two years and eight months later, the boiler pressure 
had been increased to 87 lbs. and the I. H. P. was 
over 700. 

Diagram Fig. 61 shows good economy in the use of 



216 



ENGINEERING 



steam in spite of the fact that the cut off occurs rathei 
late. There is no back pressure worth mentioning, the 
back pressure line forming part of the atmospheric 
line through the largest part of the stroke. The reason 
for this is that the areas of the exhaust ports as well 
as the exhaust pipe were sufficiently large to permit a 
free passage for the steam. The exhaust pipe, also, 
was made as short and direct as possible and all super- 
fluous elbows were dispensed with. The steam con- 




FIGURE 62. 



sumed per I. H. P. per hour as per diagram Fig. 6i 
was 22.3 lbs., and the horse power developed was 710.6. 
Figs. 62 to 64, inclusive, represent diagrams from s 
Buckeye engine 24 x 48 in., and are introduced for the 
purpose of emphasizing the need of caution and good 
judgment in setting valves by the indicator when the 
load on the engine is variable. Fig. 62, which was the 
first to be taken, would seem to indicate that the valve 
was badly adjusted, but when Fig. 63 was taken imme- 
diately afterwards, the cause of the trouble became 
apparent. The engine was furnishing power foi 



DIAGRAM ANALYSIS 



217 



operating an electric street railway on a small scale, 
and the variation in the points of cut off was caused 
by the stopping and starting of the cars. 

Fig. 63 is a notable example of the quick and deli- 
cate action of the shaft governor, as it will be seen 
that during four successive revolutions there was a 
different load each time, as shown by the diagran:. 
from the crank end. 




FIGURE 63. 



Fig. 64 was secured by quick manipulation of the 
instrument when it was known that the load was to be 
steady for a few seconds. 

Fig. 65 is from an Atlas single valve automatic cut 
off engine with shaft governor. This engine was 
16x24 in., running at 105 R. P. M., and at the time 
the diagram was taken the boiler pressure was only 50 
lbs. The spring used was a No. 30. The diagram is a 



218 



ENGINEERING 



fairly good one for the type of engine. Owing to the 
variation in the angular advance of the single eccentric 




FIGURE 64. 



actuated by a shaft governor, the degree of compres- 
sion varies with the point of cut off in the single valve 
engine, the compression being higher with an early 




FIGURE 65. 



cut off than it is when cut off occurs later in the 
stroke. The loop at A is caused by too much lead 



DIAGRAM ANALYSIS 



219 



which, together with the compression, caused a 
momentary rise in the pressure above the normal. 
The lead at B is approximately correct. The differ- 









\ 



ence in terminal pressures at C and D is the result of 
shifting of the points of cut off caused by variations in 
the load. The back pressure lines are almost identical 
with the atmospheric line, showing that the exhaust is 




FIGURE 67. 



in no way restricted or cramped. I. H. P. is 65.7 and 
steam consumption 21 lbs. per I. H. P. per hour. 

Figs. 66 and 67 are diagrams taken from a cross 



220 ENGINEERING 

compound condensing corliss engine. The high 
pressure cylinder was 24 x 48 in., and the low pressure 
cylinder was 44 x 48 in. The steam from the high 
pressure exhausted into a receiver and from thence 
into the low pressure cylinder. The receiver pressure 
was 5.3 lbs. above atmospheric pressure. The ratio of 
piston areas was 3.36 toi. That is, the area of the low 
pressure piston was 3.36 times the area of the high 
pressure piston, which was about the correct ratio for 
the pressure carried, viz., 84 lbs. gauge or 99 lbs. 
absolute. A No. 40 spring was used on the high 
pressure and a No. 12 on the low pressure cylinder. 
The number of expansions in the two cylinders was 14. 
Thus, the ratio of expansion in the high pressure cylin- 
der was 4.5 and in the low pressure the ratio was 3.1. 
Then 4.5 x 3.1 = 14; or. Thus, initial pressure = 99 lbs. 
absolute, terminal pressure in L. P. cylinder = 7 lbs. 
absolute; then 99 -f- 7 = 14. 

To illustrate the process of finding the M. E. P. with- 
out the use of ordinates w^hen the absolute initial and 
terminal pressures and the number of expansions in 
each cylinder are known, the following problems will 
be worked out: 

Find M. E. P. in L. P. cylinder. 

First, find initial pressure. 

Rule, T. P. multiplied by number of expansions. 
Thus, 7x3.1 = 21.7 lbs. absolute initial pressure in 
L. P. cylinder. 

Second, find mean forward pressure (M. F. P.). 

Rule, Multiply initial pressure by hyperbolic 
logarithm of number of expansions plus I, and divide 
product by number of expansions. Thus the hyper- 
bolic logarithm of 3.1 = 1.1314, to which add i = 2.1314. 
Then '-l:^4f^= 14.9 lbs. M. F. P. Deduct from 



DIAGRAM ANALYSIS 221 

this the back pressure, which was 5 lbs. absolute. 
Thus, 14.9— 5 = 9.9 lbs. M. E. P. in L. P. cylinder. 

Next find M. E. P. in H. P. cylinder. 

First, find T. P. in H. P. cylinder. 

This will equal the initial pressure in the L. P. 
cylinder + 2 per cent for loss in the receiver. Thus, 
21.7 4- .4 = 22.1 lbs., terminal pressure in H. P. cylinder. 

Second, find initial pressure in H. P. cylinder. 

Rule, Multiply T. P. by number of expansions. 
Thus, 22.1 X 4.5 =99.4 lbs., absolute initial pressure in 
H. P. cylinder. 

Third, find mean forward pressure (M. F. P.). 

The hyperbolic logarithm of 4.5 = 1.5041, add 
1 = 2.5041. Then ^^-^^f^^^ ^ 55 lbs., M. F. P. in H. 
P. cylinder. Deduct back pressure 22.1; thus, 55 lbs. 
-22.1 lbs. = 32.9 lbs., M. E. P. in H. P. cylinder. 

The ratio of piston areas being 3.36 to I, it may be 
of interest to pursue the subject a little farther and 
ascertain how the distribution of the steam in the two 
cylinders corresponds to the ratio of areas. The ratio 
and pressures may be expressed as follows: 
Ratio of areas — H. P. cylinder, i; L. P. cylinder, 3.36. 
M. E. P. — H. P. cylinder, 32.9; L. P. cylinder, 9.9 lbs. 
which is very nearly correct; sufficiently so for all 
practical purposes, and clearly demonstrates that with 
the intelligent use of the indicator it is possible to so 
adjust the valves and establish the points of cut off on 
a compound or triple expansion engine that the work 
done in each cylinder will be practically the same. 
As for instance, the product of the area of the H. P. 
piston and the M. E. P. = 14,883.6 lbs., and that of the 
L. P. piston X M. E. P. = 15,052.9 lbs., a difference 
of only 169.3 lbs. If the two products had been equal, 



222 ENGINEERING 

the horse power exerted in the two cylinders would 
have been the same. As it was, the horse power of 
the H. P. cylinder was 263.4 and that of the L. P. 
cylinder was 266.4, showing a difference of only three 
horse power in the amount of work done in each 
cylinder. 

Fig. 68 was taken from one of a pair of Fishkill Cor- 
liss engines connected to a common crank shaft. The 
engines were each 24 x 48 in., and run at 65 R. P. M., 
with a boiler pressure of 65 lbs. They were equipped 
with a jet condenser and a bucket plunger air pump 
served for both engines. These engines had been in 




FIGURE 68 



continuous service for nearly seventeen years when the 
author was called upon to indicate them and adjust 
the valves. A diagram taken at the same time from 
the mate of this engine was very nearly an exact 
counter part of Fig. 68. The horse power, as shown 
by Fig. 68, was 248, and the steam per I. H. P. per 
hour was 15.2 lbs. The vacuum gauge showed 2J in. 
and a 50 spring was used. 

Figs. 69 and 70 are from an old Fishkill corliss 
engine 16x42 in., to which the author applied the 
indicator after he had set the valves, according to the 
ordinar}^ rules for valve setting, by the marks placed 



DIAGRAM ANALYSIS 



223 



on the ends of the valves and valve chests. These 
diagrams are introduced especially for the purpose of 
showing the need of exercising the greatest of care to 
prevent dirt or grit of any kind from getting into the 




FIGURE 69. 

indicator cylinder. After the indicator pipes had been 
blown out sufficiently, as it was thought, the indicator, 
which was a thoroughly reliable instrument, was 
attached and diagram Fig. 69 was obtained. It 
showed the valve adjustment to be very nearly correct, 
but the perfectly straight steam lines and the sharp 




FIGURE 70. 



corners and sudden drop at cut off were a puzzle, espe- 
cially in an old engine where the valves and valve 
seats were known to be much worn down. After 
taking several more diagrams with precisely the same 



224. ENGINEERING 

result, the indicator was removed, and upon taking 
out the piston a quantity of dirt was found on it and 
also on the inside of the cylinder. This fully 
explained the cause of the sharp corners, etc., on the 
diagram. After the indicator had been cleaned and 
oiled it was again connected and Fig. 70 was produced, 
w^hich is a truthful presentation of the performance of 
the steam in the cylinder. 

Many diagrams are- misleading, owing to causes 
similar to the above, and a diagram with too sharp 
angles at cut off or release should be regarded with 
suspicion until it is proved beyond all doubt to be 
truthful. 




FIGURE 71. 

Fig. 71 represents a diagram from a vertical non- 
condensing engine 14 x 16 in. with riding cut off, 
which the author was called upon to adjust. This 
engine was nearly new, having been run but a few 
months, and although the size of it was ample to do 
all the work required, yet it had failed, so far, to supply 
one-half the power needed. After taking the diagram 
and making a few outside investigations, the cause of 
the trouble was apparent. Indeed, the wonder was that 
the engine had supplied as much power as it had 
under the circumstances. 

First. It was situated too far from the boiler plant, 
being fully 1,200 ft., and although a pressure of 85 lbs. 



DIAGRAM ANALYSIS 225 

was carried at the boilers and the steam was conveyed 
through a 6-inch pipe, yet owing to the many drains on 
the pipe for heating buildings, running other small 
engines, etc., by the time the steam reached the engine 
in question the pressure was reduced so much that a y 
spring was found to be too strong, although that wa- 
the scale of Fig. 71. 

Second, the end of the exhaust pipe was found to 
be submerged in a nearby pond of water to which J 
had been carried, probably with a view of making, 
condensing engine out of it! It was also found tha 




FIGURE 72. 

there were no less than four superfluous elbows in tb 
exhaust pipe that could easily be dispensed with. The 
diagram shows that the cut off was practically useless 
That the back pressure was nearly 6 lbs. above th 
atmosphere, and that the engine was using 55 lbs. o^ 
steam and 7 lbs. of coal per horse power per hour, ail 
of which conditions were about as bad as they coula 
be. 

After increasing the lead and adjusting the cut off a 
No. 16 spring was used and Fig. 72 was produced 
which, although still showing late admission, is an 
improvement over the original diagram. The initial 



226 ENGINEERING 

pressure being only 30 lbs. above the atmosphere, 
further work with the indicator was deferred until 
changes were made in the steam and exhaust pipes, 
by which the initial pressure was increased to 55 lbs. 
and the exhaust pipe was freed of extra turns and 
raised from its watery grave into the open air. The 
engine has since then given perfect satisfaction. 

Fig. 73 is from a Buckeye automatic cut off engine 
18 X 36 in. The engine had been running for several 
years with the valves in the condition shown by the 
diagram, and in the meanwhile, the load having been 
increased from time to time, the engine finally refused 




FIGURE 73. 

to run up to speed and something had to be done. 
The superintendent of the plant said that he had an 
idea that something was the matter with the engine 
but could not ascertain what it was, and so he finally 
called upon the author to apply the indicator. The 
result was that diagram Fig. 73 was obtained, showing 
that the principal cause of the trouble was unequal cut 
off. After equalizing the cut off and increasing the 
lead on the crank end by a small fraction diagram 
Fig. 74 was taken, and after this the engine gave no 
further trouble. The depression in the steam lines 
might have been rectified to some extent by increasing 



DIAGRAM ANALYSIS 227 

the boiler pressure, thus giving a higher initial pressure 
and an earlier cut off. The speed of the engine was 
94 R. P. M., with a boiler pressure of 70 lbs. A 40 
spring was used with the indicator. 

In order to more fully illustrate the process of ascer- 
taining the M. E. P. without dividing the diagram into 
ordinates, the following computation is given together 
with rules, etc. In this process two important factors 
are necessary, viz., the absolute initial pressure and 
the absolute terminal pressure, and they can both be 
obtained from the diagram by measuring with the 




FIGURE 74. 

scale adapted to the spring used. Thus, in Fig. 74 the 
absolute initial pressure measured from the line of 
perfect vacuum V to line B is "jj lbs., and the absolute 
terminal pressure measured from V to line B' is 21 lbs. 
The ratio, or number of expansions, is found thus: 

Rule, Divide the absolute initial pressure by the 
absolute terminal pressure; thus, yy -^ 21 =^ 3.65 = num- 
ber of expansions. 

Second. Find mean forward pressure. 

Rule. Multiply absolute initial pressure by the 
hyperbolic logarithm of number of expansions plus i, 
and divide product by number of expansions. Thus, 



228 



ENGINEERING 



referring to Table 8, it will be seen that the hyperbolic 
logarithm of 3.65 is 1.2947, to which i must be 
added. Then ^-^-^^^ — = 48.4 lbs., which is the abso- 
lute mean forward pressure. From this deduct 
the absolute back pressure, which is 16 lbs. or i lb. 
above atmosphere; thus, 48.4- 16= 32.4 lbs. M. E. P. 

Third. Find I. H. P. 

Area of piston minus one-half area of rod x M. E. P. 
X piston speed in feet per minute, divided by 33,000. 
Thus (the diameter of rod being 3 in.), "^-""^a^'^"^ = 
138.9 I. H. P. 

The steam consumption per I. H. P. per hour may 
also be computed by means of Table 10, which was 
originally calculated by Mr. Thomson, and is based 
upon the following theory: 

TABLE 10. 



T. P. 


w. 


T. P. 


W. 


T. P. 


W. 


3 


117.30 


13 


466.57 


23 


798.10 


3-5 


135.75 


13.5 


483.43 


23.5 


814.39 


4 


153.88 


14 


500.22 


24 


830.64 


4.5 


171.94 


14.5 


517.07 


24.5 


846.96 


5 


186.75 


15 


533.85 


25 


863.25 


5.5 


207.60 


15.5 


550.64 


25.5 


879.49 


6 


225.24 


16 


567.36 


26 


895.70 


6.5 


242.97 


16.5 


584.10 


26.5 


911.86 


7 


260.54 


17 


600.78 


27 


927.99 


7.5 


278.06 


17.5 


617.40 


27.5 


944.07 


8 


295.44 


18 


633.96 


28 


960.12 


8.5 


312.80 


18.5 


650.46 


28.5 


976.27 


9 


330.03 


19 


666.90 


29 


992.38 


9-5 


347.27 


19.5 


683.38 


29.5 


1008.46 


10 


364.40 


20 


699.80 


30 


1024.50 


10.5 


381.57 


20.5 


716.27 


30.5 


1040.51 


II 


398.64 


21 


732.69 


31 


1056.48 


/1. 5 


415.73 


21.5 


749.06 


31.5 


1072.42 


IZ 


432.72 


22 


765.38 


32 


1088.32 


t2.S 


449.69 


22.5 


781.76 


32.5 


1104.35 



DIAGRAM ANALYSIS 229 

A horse power = 33,000 ft. lbs. per minute, or 1,980,- 
000 ft. lbs. per hour, or 1,980,000 x 12 = 23,760,000 in. 
lbs. per hour, meaning that the same amount of energy 
required to lift 33,000 lbs. one foot high in one minute 
of time would lift 23,760,000 lbs. one inch high in one 
minute of time. Now if an engine were driven by a 
fluid that weighed one pound per cubic inch, and the 
mean effective pressure of this fluid upon the piston 
was one pound per square inch, it would require 
23,760,000 lbs. of the fluid per horse power per hour. 
But, if in place of the heavier fluid we substitute pure 
distilled water of which it requires 27.648 cu. in. to 
weigh one pound, the consumption per I. H. P. per 
hour will be considerably less; as, for instance, 23,760,- 
000 H- 27.648 = 859,375 lbs., which would be the rate 
per hour of the water driven engine if the M. E. P. of 
the water was one pound per square inch and if the 
M. E. P. was increased to 20 lbs.; then twenty times 
more power would be developed with the same volume 
of water, but the weight of water consumed per H. P. 
per hour would be proportionately less. Now if the 
engine is driven by steam it will consume just as 
much less water in proportion as the water required to 
make the steam is less in volume than the steam used. 
Therefore if the above constant number, 859,375, be 
divided by the M. E. P. of any diagram and by the 
volume of the terminal pressure, the quotient will be 
the water (or steam) consumption per I. H. P. per 
hour. 

Referring to Table 10, the numbers in the W columns 
are the quotients obtained by dividing the constant, 
859,375, by the volumes of the absolute pressures 
given in the columns under T. P. and which represent 
terminal pressures. The table is considerably abridged 



230 ENGINEERING 

from the original, which was very full and complete, 
Ihe pressures advancing by tenths of a pound from 3 
bs. to 60 lbs.; but it is seldom that in ordinary practice 
there is needed such accuracy. If at any time, how- 
ever, a diagram should show a terminal pressure not 
given in the table, the correct factor for that pressure 
can be easily found by dividing the constant 859,375, 
by the relative volume of the pressure as found in 
Table 5 of the properties of saturated steam given in 
another chapter. 

Referring again to Fig. 74, it is seen that the ter- 
minal pressure is 21 lbs. absolute, and by reference to 
Table 10 and glancing down column T. P. until 21 is 
reached, it will be seen that the number opposite in 
column W is 732.69. This number divided by the M. 
E. P. of the diagram Fig. 74, which is 32.4 lbs., gives 
22.6 lbs. per I. H. P. per hour as the steam consump- 
tion. The rate thus found makes no allowance for 
clearance and compression, however, and these two 
very important items will be treated in a succeeding 
chapter together with the method of correction for the 
above, viz., clearance and compression, as they enter 
largely into the steam economy of an engine. 

Questions 

1. What effect has back pressure upon the work of 
an engine? 

2. Name some of the causes of wire drawing of the 
steam. 

3. What relation should the steam line of an indi- 
cator diagram bear to the atmospheric line? 

4. What is the effect of insufificient lead upon the 
admission line of a diagram? 



DIAGRAM ANALYSIS 231 . 

5. How does an unequal cut off affect the working 
of an engine? 

6. How is the number of expansions in a compound 
engine ascertained? 

7. What is the rule for finding the initial pressure by 
calculation? 

8. Give the rule for finding the mean forward 
pressure. 

9. When the M. F. P. is known^ how may the mean 
effective pressure be found? 

10. How should the steam be distributed in the 
cylinders of a compound engine? 

11. What is the rule for finding the horse power 
developed by an engine? 

12. What is meant by the steam consumption of an 
engine? 

13. What is considered an economical rate of steam 
consumption for a non-condensing engine? 

14. What is a fairly good rate of steam consumption 
for a condensing engine? 



CHAPTER X 

DIAGRAM ANALYSIS— CONT/NC/ED 

Diagram analysis continued — Corliss Centennial engine and dia° 
grams from it — Calculating steam consumption from indicator 
diagrams — Clearance and compression, and how to correct a 
diagram for the same — How to estimate the theoretical clear- 
ance from a diagram — Measuring the volume of the clearance 
space with water — The theoretical expansion curve — Illustra- 
tion of hyperbolic law in its appHcation to the expansion of 
gases — The adiabatic curve and how to draw it — Power cal- 
culations — Method of finding the M. E. P, of a diagram — The 
plani meter and how to use it. 

Figs. 75 to 77 are reproductions of diagrams taken 
by the author from the once famous engine built by 
Geo. H. Corliss for the Centennial Exposition which 
was held at Philadelphia in 1876. A brief description 
of this engine may not be out of place here, as it will 
enable the reader to study the diagrams to a better 
advantage. 

This engine is, in fact, two simple condensing beam 
engines, exactly alike in every detail, standing verti- 
cal side by side and connected to a common crank 
shaft by means of the working beams overhead which 
are pivoted at their centers to the A frame of the 
engine. The cylinders are 40 in. bore by 10 ft. stroke 
and the engine runs at a speed of 36 R. P. M., thus 
giving a piston speed of 720 ft. per minute. The valve 
gear is of the regular corliss type adapted to a vertical 
engine, and motion is transmitted from the eccentric 
through the medium of a rock shaft placed horizontally 
on the frame. The steam and exhaust valves are 

232 



DIAGRAM ANALYSIS 



located in the cylinder heads, thereby reducing the 
clearance to 1.5 per cent. Each engine has its own 
jet condenser and air pump, which latter is of the 
regular bucket plunger type and receives its motion 
from the overhead beam through long connecting rods. 
The crank shaft is 18 in. in diameter and carries a gear 
fly-wheel 30 ft. in diameter, weighing 56 tons, the 
teeth of which mesh into another gear wheel 10 ft. in 
diameter carried on the jack shaft through which the 
power is transmitted to the various departments of the 
works. The face of the rim of the gear wheel is 24 in. 




FIGURE 75 



in width, which allows the length of the teeth to be 
24 in., while the pitch, or distance from center to cen- 
ter of the teeth, is 5 in. The steam pipe is 18 in. inside 
diameter and the cylinders are jacketed with live 
steam. 

This engine showed remarkable economy in the use 
of steam when working at or near the capacity for 
which it was designed by Mr. Corliss, which was 1,400 
horse power. At the time Fig. 75 was taken the load 
was 1,122 horse power and the boiler pressure was 32,5 
lbs. gauge, or 47.5 lbs. absolute. The spring used was 



£34 



ENGINEERING 



a No. 20, although a much better appearing diagram 
would hav^e been obtained by using a No. 30 spring. 

The diagram shows very slight compression, but the 
lead is correct. The point of cut off is not so clearly 
defined as it should be, and the author attributes the 
cause of this to the spring being too weak for the 
reason that when Fig. 76 was taken some eight months 
later from the same end of the same cylinder, but with 
a spring of the proper tension for the pressure, the 
point of cut off is much more plainly defined. (See 
Fig. 76.) 




FIGURE 76. 

The absolute initial pressure, as shown by Fig. 75, 
was 47.5 lbs., and the absolute terminal pressure was 
8.5 lbs. The ratio of expansion would therefore be 
47-5 ^ 8-5 = S-6. The steam consumption per I. H. P. 
per hour was 14 lbs. 

Fig. ']J is from the same engine, and is here intro- 
duced for the purpose of showing the great adv^antage 
resulting from a good vacuum. In fact the largest 
portion of the work in this case was done through the 
help of the vacuum, as indicated by much the largest 
portion of the area of the diagram being below the 
line of atmospheric pressure. The diagram would 
appear to be a kind of connecting link between the 



DIAGRAM ANALYSIS 



2S5 



times of Watt and Newcomen, when the vacuum did 
all the work, and these modern times of high steam 
pressure. 

The circumstances under which Fig. yy was obtained 
were as follows: At certain times it became necessary 
to run a part of the shops overtime, and the load at 
such times being light, the boiler pressure was allowed 
to drop to the point at which the engine would run the 
most quietly, and that point was found to be about 7 
lbs. gauge pressure. A No. 10 spring was used. The 
horse power developed was 227.5, which multiplied by 




FIGURE 77. 



2, as there were two engines, would equal 455 I. H. P. 
But the rate of steam consumption, which was 
23.3 lbs. per I. H. P. per hour, was considerably 
higher than it was with the ordinary load, as when 
Fig. 75 was taken, showing that it is very poor econ- 
omy to run an engine very much below its rated 
capacity. 

F'ig. 78 is from a Hamilton corliss non-condensing 
engine 325^ in. bore by 72 in. stroke. A No. 60 spring 
was used, the boiler pressure being 85 lbs. gauge. The 
I. H. P. was 652.2 and the steam consumption per 
I. H. P. per hour was 22.9 lbs. 



236 ENGINEERING 

There are but few points about the diagram that are 
open to criticism. The compression is rather high for 
so large an engine and the steam lines should be main- 
tained more nearly horizontal up to the point of cut 
off. 

Steam Consumption from Indicator Diagrams. In cal- 
culating the steam consumption of an engine, two very 
important factors must not be lost sight of, viz., clear- 
ance and compression. Especially is this the case in 
regard to clearance when there is little or no compres- 
sion, for the reason that the steam required to fill the 
clearance space at each stroke of the engine is prac- 




-4 



FIGURE 78. 

tically wasted, and all of it passes into the atmosphere 
or the condensor, as the case may be, without having 
done any useful work except to merely fill the space 
devoted to clearance. On the other hand, if the 
exhaust valve is closed before the piston completes 
the return stroke, the steam then remaining in the 
cylinder will be compressed into the clearance space 
and can be deducted from the total volume which, 
without compression, would have been exhausted at 
the terminal pressure. 

Figs. 79 and 8o, which are reproductions of diagrams 
taken by the author while adjusting the valves on a 
16x42 in. Corliss engine, will serve to graphically 



DIAGRAM ANALYSIS 



237 



illustrate this point. Fig. 79, which was the first one 
to be taken, shows no compression. The point of 
admission at A is plainly defined by the square corner 
at the extreme end of the stroke. The clearance of 




FIGURE 79. 



this engine is 4 per cent, of the volume of the piston 
displacement. The engine being 16 in. bore by 42 in. 
stroke, the piston displacement is found by the follow- 
ing calculation: Area of piston, 201.06 sq. in. x stro^'*. 




FIGURE 80. 



42 in. =8444.52 cu. in. The volume of clearance 
space is equal to 8444.52 cu. in. x .04 = 337.78 cu. in., 
which divided by 1,728 = .195 cu. ft. 

By reference to Fig. 80, taken after adjusting the 



iSS ENGINEERING 

v^alves for compression, it will be noticed that the 
steam is there compressed to s7 lbs., the compression 
curve beginning at C and ending at B. There is 
therefore compressed during each stroke a volume of 
steam equal to .195 cu. ft. at a pressure of 37 lbs. 
gauge, or 52 lbs. absolute. 

One cubic foot of steam at 52 lbs. absolute pressure 
weighs .1243 lbs., and .195 cu. ft. will weigh .1243 x 
.195 = .0242 lbs. 

The engine was running at 70 R. P. M., or 140 
strokes per minute. Thus, according to Fig. 80, the 
total weight of steam compressed and doing useful 
work during one hour, and which without compression 
would have passed out through the exhaust pipe, is 
equal to .0242 x 140 x 60 = 203.28 lbs. 

Now in order to estimate the steam consumption of 
the above engine from diagram Fig. 79, it would be 
necessary to account for all the steam occupying not 
only the volume of the piston displacement at the end 
of the stroke, but the clearance as well, for the reason, 
as before stated, that it would all be released before 
exhaust closure. This would equal 8444.52 cu. in. 
+ 337-78 cu. in = 8782.3 cu. in., which divided by 
1,728=5.08 cu. ft. each stroke, or 10.16 cu. ft. each 
revolution. 

The absolute terminal pressure of Fig. 79 is 20 lbs. 
One cubic foot of steam at this pressure weighs .0507 
bs., and the weight t>i steam consumed each revolu- 
tion would therefore be 10.16 x .0507 = .515 lbs., which 
multiplied by 70 R. P. M. = 36.05 lbs. per minute, or 
2,163 lt)s. per hour. The horse power developed by 
the engine at the time was 80. Therefore the steam 
consumption per I. K. P. per hour = 2, 163 -^ 80 = 27 
lbs. 



DIAGRAM ANALYSIS 

Referring again to Fig. 80 it will be remembered 
that the total weight of steam compressed during one 
hour was 203.28 lbs. The weight of steam consumed 
per hour, therefore, equals 2,163 — 203.28= 1959.7 lbs. 

Owing to compression, the work area of Fig. 80 is 
somewhat smaller than that of Fig. 79, amounting in 
fact to the area of the irregular figure enclosed between 
the points A, B and C. The work represented by this 
figure amounts to a very small proportion of the total 
work indicated by Fig. 79, still in order to arrive at 
correct conclusions, it should be deducted therefrom. 

Assuming the negative work to be equal to .55 horse 
power, we have 80 — .55 = 79.45 I. H. P. as the work 
represented by Fig. 80. As the total weight of steam 
consumed in one hour was 1959.7 lbs., the steam con- 
sumption per I. H. P. per hour will be 1959.7 -f- 
79.45 = 24.67 lbs., a saving by compression of 2.33 lbs. 
per H. P. per hour, besides the great advantage of 
having a cushion of steam in contact with the piston at 
the termination of the stroke, thus bringing the mov- 
ing parts of the engine to rest quietly without shock 
or jar. 

The steam consumption may also be computed from 
the diagram, regardless of the dimensions of the 
cylinder or the horse power developed. The mean 
effective pressure and also the absolute terminal pres- 
sure must, however, be known. This method was 
referred to in the preceding chapter, but in the com- 
putation therein made no correction was made for 
clearance and compression. 

Having reviewed these two factors at considerable 
length it will now be in order to more fully explain 
the methods of treating diagrams when it is desired to 
make these corrections. 



240 ENGINEERING 

First, draw vertical lines C and D, Fig. 8i, at each 
end of the diagram, and perpendicular to the atmos- 
pheric line. Draw line V, representing perfect vacuum, 
14.7 lbs. below the atmospheric line, as indicated on 
the scale adapted to the diagram, which in this case is 
50 lbs. to the inch. Continue the expansion from R, 
where release begins, until it intersects line D V, from 
which point the absolute terminal pressure can be 
measured. 

Having ascertained the terminal pressure, which for 
Fig. 81 is 30 lbs., draw line D E, which may be called 




I I 
—J Li^ 

FIGURE 81. 

the consumption line for 30 lbs. The terminal 
being 30 lbs., refer to Table 10 and find in column VV, 
opposite 30 in column T. P., the number 1,024.5. 
Divide this number by the M. E. P which in Fig. 81 is 
41 lbs., and the quotient, which is 24.99 lt)s., is the 
uncorrected rate of steam consumption. This rate 
stands for the total consumption throughout the whole 
stroke represented on the diagram by the distance 
from D to C, which measures 3.25 in., but it is evident 
that there is a small portion of the return stroke, that 
indicated by the distance from E to C, during which 



DIAGRAM ANALYSIS 241 

the steam compressed in the clearance space should 
not be charged to the consumption rate, but should 
be deducted therefrom. In order to do this, 
multiply the uncorrected rate by the distance from D 
to E, which is ^}i in, or 3.125 in., and divide the pro- 
duct by the distance from D to C, 3^ in., or 3.25 in. 
Thus, 24.99 ^ 3-1^5 "^ S-^S = 24.03 lbs., which is the cor- 
rected rate and represents a saving by compression of 
24.99 — 24.03 = .96 lbs., or nearly 3.7 per cent. 

In many cases the terminal pressure greatly exceeds 
the compression, an illustration of which is given in 
Fig. 82 which is a reproduction of a diagram from an 



FIGURE 82. 

old Wheelock engine. It now becomes necessary to 
extend the compression curve to L, a point equidistant 
from the vacuum line with the terminal at R. The 
consumption line R. L. now becomes longer than the 
stroke line R. M., therefore the corrected rate will 
exceed the uncorrected rate by just so much; as for 
instance, terminal pressure = 34 lbs. The factor, as 
per Table 10, = 1152.26, and the M. E. P. of the diagram 
is 47 lbs. Then, 1,152.26-^47 = 24.5 lbs., uncorrected 
rate; 24.5x3.125 in. (distance R. L.)-4-3 in. (distance 
R. M.) = 25.52 lbs., corrected rate, a loss of a little 
more than one pound, or about 4 per cent. 



242 ENGINEERING 

There is another class of diagrams very frequently 
encountered in which the terminal pressure is con- 
siderably below the compression curve, and in order to 
compute the consumption rate by the above method it 
becomes necessary to continue the compression curve 
downwards until it meets the terminal, as illustrated at 
A, Fig. 83, which is a friction diagram from a Buckeye 
engine. R is the point of release, D A represents the 
consumption line, and D C the stroke. The terminal 




FIGURE 83. 

is 8.5 lbs., and the factor for that pressure, accordmg 
to Table 10, is 312.8. Dividing this number by the M. 
E. P., which was 7 lbs., gives 44.6 lbs. as the uncor- 
rected rate. The distance D to A, where the com- 
pression curve intersects the consumption line, is 
2.625 in., and the total length of the diagram C to 
D is 3.375 in. Then 44.6x2.625-^3.375 = 35 lbs. as 
the corrected rate. The extremely high rate is owing 
to the fact that the engine was running light, no load 
except a line of empty shafting. 



DIAGRAM ANALYSIS 24S 

Theoretical Clearance. The expansion and compres- 
sion curves of a diagram are created by the expansion 
and compression of all the steam admitted during the 
stroke. This includes the steam in the clearance space 
as well as in the cylinder proper. It is evident, 
therefore, that the volume of the clearance is one of 
the factors controlling the form of these curves, and 
when the clearance is known a correct expansion or 
isothermal curve may be theoretically constructed, as 
will be explained later on. Also if the actual curves, 
either expansion or compression, of a diagram assume 
an approximately correct form, the clearance, if not 
already known, may be determined theoretically from 
them; although too much confidence should not be put 
in the results as they are liable to show either too little 
or too much clearance, generally the latter, especially 
if figured from the compression curve. 

For the benefit of those who may desire to test this 
method of ascertaining the percentage of clearance of 
their engines, several illustrations will be given of its 
application to actual diagrams taken from engines in 
which the clearance was known. 

Fig. 84 is from an engine in which the clearance 
was known to be 5 per cent. As compression cuts but 
a very small figure in this diagram, the expansion 
curve alone will be utilized for obtaining the theoreti- 
cal clearance, and the process is as follows: 

Select two points, C and R, in the curve as far apart 
as possible, but be sure that they are each within the 
limits of the true curve. Thus C is located just after 
cut off takes place, and R is at a point just before 
release begins. From C draw line C D parallel with 
the atmospheric line. From D draw line D R, and 
from C draw line C E, both perpendicular to the 



244 



ENGINEERING 



atmospheric line. Then from R draw line R E, form* 
ing a rectangular parallelogram, C D R E, with two 
opposite corners, C and R, within the curve. Now 
through the other two corners, D and E, draw the 
diagonal D E, extending it downwards until it inter- 
sects the vacuum line V. From this point erect the 
vertical line V W, which is the theoretical clearance 
line. 

To prove the result proceed as follows: Measure 
the length of diagram from F to G, which in this case 



yy 




FIGURE 84. 



is 3.75 in., representing piston displacement. Next 
measure the distance from F to the clearance line V W, 
which is 3.91 in., representing piston displacement 
with volume of clearance added. Then 3.91—3-75 = 
.16, which represents volume of clearance; and .i6x 
100 - 3.75 = 4.3 per cent., which is approximately near 
the actual clearance, which, as before stated, was 5 per 
cent. 

Fig. 85 serves to illustrate the same method applied 
to the compression curve. This diagram is a repro- 



DIAGRAM ANALYSIS 



245 



diiction of one taken from the low pressure cylinder of 
a large compound condensing corliss engine in which 
the actual clearance was 2.25 per cent. Two points, G 
and H, are selected in the compression curve, and 
from them the parallelogram G H I K is erected 
with two of its opposite corners, G and H, well within 
the limits of the curve, while through the other two 
corners, I and K, the diagonal I K C is drawn 
intersecting the vacuum line at C, thus locating the 




FIGURE 85. 



point from which the clearance line C D can be drawn. 
The measurements in this case are as follows: 

Total length of diagram, E to F = 3.75 in. 

Distance from clearance line, DC, to F = 3.875 in. 

Volume of clearance = 3.875 — 3-75 = . 125 in. 

. 125 X 100 -^ 3.75 = 3.33 per cent, clearance, which is 
1.08 per cent, more than the known clearance. 

However, notwithstanding the liability to error in 
many cases, still this method of computing clearance 
may often be utilized to good advantage. 

Another and more practical method of measuring 
clearance is as follows: Place the engine on the dead 
center. Remove the valve chest cover and take out 
the valve. Close the cylinder cock on that end of the 
cylinder to which the piston has been moved, leaving 



246 ENGINEERING 

the cock on the opposite end of the cylinder open and 
disconnected from its drip pipe, so as to give an 
opportunity for catching any water that may leak past 
the piston while measuring the clearance space. Then 
having first provided a known weight of w^ater, always 
making sure of having a little more than enough, pour 
it into the steam port until the clearance space is filled 
to a level with the valve seat. When this is done, 
weigh the water that is left and deduct it from the 
original quantity, and the remainder will be the num- 
ber of pounds of water required to fill the clearance, 
from which it is an easy matter to compute the number 
of cubic inches or cubic feet in the space devoted to 
clearance. If any water leaks past the piston during 
the operation it should be weighed and deducted from 
the total quantity poured into the port. 

In the case of an engine having the valve chest on 
the side of the cylinder it will be necessary to close 
the steam port either by blocking the valve against it 
or by fitting a piece of soft wood into it, making it 
water tight. The water can then be poured into the 
clearance space through a pipe conncted to the indi- 
cator opening in that end of the cylinder. Care should 
be exercised to allow a vent for the air to escape as it 
is displaced b}^ the water. 

The Theoretical Expansion Curve. According to 
Boyle's law the volume of all elastic gases is inversely 
as their pressures, and steam being a gas conforms sub- 
stantially to this law; although the expansion curves 
of indicator diagrams are affected more or less by the 
loss of heat transmitted through the cylinder walls, 
and by the change in the temperature of the steam 
produced by the changes in pressure during the prog- 
ress of the stroke. The pressure generally falls more 



DIAGRAM ANALYSIS 



247 



rapidly during the first part of the stroke, and less 
rapidly during the last portion than it should in order 
to conform strictly to the above law, and the terminal 
pressure usually is greater than it should be to agree 
with the ratio of expansion. But this fullness of the 
expansion curve of the diagram near the end compen- 
sates in a measure for the too rapid fall near the begin- 
ning of the stroke. Therefore, if the engine is in 
fairly good condition with the valves properly adjusted 
and not leaking, and the piston rings are steam tight, 



J 




j 

f 

/ 


1 ==4^ 







Af 



FIGURE 86. 



J3 C^ A 



it may be assumed that the expansion of the steam in 
the cylinder takes place according to Boyle's law and 
it is found that the expansion curve drawn by the indi- 
cator practically coincides with a hyperbolic curve 
constructed according to that law. 

Fig. 86 graphically illustrates the application of the 
hyperbolic law to the expansion of gases. The hori- 
zontal lines represent volumes and the vertical lines 
represent pressures. The base line, A F, represents 
the full stroke of a piston in the cylinder of an engine, 



248 ENGINEERING 

and the vertical line A I represents the pressure of 
the steam at the commencement of the stroke. 

Suppose there is no clearance and that the steam has 
been admitted up to point H when it is cut off. The 
rectangle A B H I is the product of the pressure mul- 
tiplied by the volume of the steam thus admitted. 
When the piston has traveled from A to C the volume 
of the steam has been doubled and the pressure C L 
has been reduced to just one-half what it was at A I, 
but the area of the rectangle A C L M is equal to the 
area of the initial rectangle, and, as before, is the pro- 
duct of the pressure C L multiplied by the volume A C. 
As the piston travels still farther, as from A to D, the 
steam is expanded to four volumes while the pressure 
at D K will only be one-fourth that of the initial 
pressure; but the new rectangle A D K N is still equal 
in area to either of the others, ABHIorACLM. 

The same law applies to each of the remaining rect- 
angles; A E G O representing five volumes and one- 
fifth of the initial pressure, and A F R P representing 
six times the initial volume and one-sixth of the initial 
pressure, but each having the same area as the initial 
rectangle A B H I. Now the area of the rectangle 
A B H I represents the work done by the steam up to 
the point of cut off, and the area of the hyperbolic fig- 
ure enclosed by the lines B H R F represents the work 
done by the expansion of the steam after cut off 
occurs. This area and the amount of work it repre- 
sents may be computed by means of the known rela- 
tions of hyperbolic surfaces with their base lines; as 
for instance, if the base lines A B, A C, A D, etc., 
extend in geometrical ratio, as i, 2, 4, 8, 16, etc., the 
successive areas, BHLC, BHKD, BHGE, etc., 
increase in arithmetical ratio, as i, 2, 3, 4, etc. 



DIAGRAM ANALYSIS 



249 



On the principles of common logarithms, which 
represent in arithmetical ratio natural numbers in 
geometrical ratio, tables of hyperbolic logarithms have 
been computed for the purpose of facilitating the cal- 
culation of areas of work due to different degrees of 
expansion. Such a table is given elsewhere in this 
book, and in Chapter IX is described the method of 
calculating the M. E. P. by this means. 

A theoretical curve may be constructed conjointly 
with the actual expansion curve of a diagram by first 
locating the clearance and vacuum lines and then pur- 




FIGURE 87. 



suing the method illustrated by Fig. 87. A curve so 
produced is called an isothermal curve, meaning a 
curve of the same temperature. 

Referring to Fig. 87, suppose, first, that it is desired 
to ascertain how near the expansion curve of the dia- 
gram coincides with the isothermal curve, at or near 
the point of cut off. Select point R near where 
release begins, but still well within the expansion 
curve. From this point draw the vertical line, R T, 
parallel with the clearance line, V S. Then draw the 
horizontal line, S T, parallel with the atmospheric line, 



250 ENGINEERING 

and at such a height above it as will equal the boiler 
pressure as measured by the scale adapted to the dia- 
gram; such measurement to be made from the atmos- 
pheric line to correspond with the gauge pressure. 
From T draw the diagonal T V, and from R draw the 
horizontal line R D parallel with the atmospheric line. 
From D, where this line intersects T V, erect the 
perpendicular D E, thus forming the parallelogram 
R D E T, and as line T V passes through two of its 
opposite angles and meets the junction of the clear- 
ance and vacuum lines, the other two angles, R and 
E, will be in the theoretical curve, and R being the 
starting point, it is obvious that this curve must pass 
through E, which would be the theoretical point of 
cut off on the steam line S T. 

Two important points in the theoretical curve have 
now been located, viz., E as the cut off, and R as the 
point of release. In order to obtain intermediate 
points, draw any desired number of lines downward 
from points in S T, as i, 2, 3, 4, 5, etc., and continue 
them downwards far enough to be sure that they will 
meet the intended curve, and from the same points in 
S T draw diagonals i V, 2 V, 3 V, 4 V, 5 V, etc., all 
to converge accurately at V. From the intersection of 
these diagonals with D E draw horizontal lines paral- 
lel with V V\ and the points of junction of these lines 
with the vertical lines will be points in the theoretical 
curve. It will now be an easy matter to trace the 
curve through these points. If, on the other hand, it 
be desired to compare the curves toward the exhaust 
end of the diagram, draw lines E D and E T, Fig. 88, 
also T R, locating R near where release commences, 
after which draw line R D, completing the parallelo- 
gram E T R D, fixing R as a point in the theoretical 



DIAGRAM ANALYSIS 



251 



curve started at E. After drawing the diagonal T V, 
proceed in the same manner as before to locate the 
intermediate points. 

It will be observed that in order to ascertain the 
performance of the steam near the beginning of the 
stroke, the starting point of the isothermal curve must 
be near the point of release, and conversely, n tcft 
starting point of the curve is located near the poini of 
cut off and coincident wnth the actual curve, the test 
will apply towards the end of the stroke. It is not to 
be expected that the expansion curve of any diagram 
taken in practice will conform strictly to the lines of 




FIGURE 88. 



the isothermal curve, especially towards the latter end 
of the stroke, owing to the reevaporation of water 
resulting from the condensation of steam which was 
retained in the cylinder by the closing of the exhaust 
valve. This reevaporation commences just as soon as 
the temperature of the steam, owing to reduction of 
pressure due to expansion, falls below the temperature 
of the cylinder walls, and it continues at an increasing 
rate until release occurs. The tendency of this 
reevaporation or generation of steam within the 
cylinder during the latter portion of the stroke is to 



252 



ENGINEERING 



raise the terminal pressure considerably above what it 
would be if true isothermal expansion took place. 
The terminal pressure may also be augmented by a 
leaky steam valve, while, on the other hand a leaky 
piston would cause a lowering of the terminal and an 
increase in the back pressure. 

The Adiabatic Curve. If it were possible to so pro- 
tect or insulate the cylinder of a steam engine that 
there would be absolutely no transmission of heat 
either to or from the steam during expansion, a true 
adiabatic curve or "curve of no transmission'' might 



4^ 



Z2: 



izi 




5q 

HS 



zL 



FIGURE 89. 



be obtained. The closer the actual expansion curve 
of a diagram conforms to such a curve, the higher will 
be the efficiency of the engine as a machine for con- 
verting heat into work. 

Fig. 89 illustrates a method of figuring a curve 
which, while not strictly adiabatic, will be near 
enough for all practical purposes, while at the same 
time it will give the student an opportunity to study 
the laws governing the expansion of saturated steam." 

To draw the curve, first locate the clearance and 
vacuum lines V S and V V. Next locate point R in 



DIAGRAM ANALYSIS 25S 

the expansion curve near where release begins, making 
this the starting point, and also the point of coinci- 
dence of the expansion curve with the adiabatic curve. 
The other points in the curve are located from the 
volumes of steam at different pressures during expan- 
sion; the pressures being measured from the line of 
perfect vacuum, and the volumes from the clearance 
line. 

The absolute pressure at R, Fig. 89, is 26 lbs. From 
point R erect the perpendicular R T. Also draw hori- 
zontal line R 26 parallel with the vacuum line and at a 
height equal to 26 lbs. above vacuum line V V, as 
shown by the scale, which in this case was 40. The 
length of line R 26, measured from R to the clearance 
line, is 3^^ in., or 3.0625 in. By reference to Table 5 
it will be seen that the volume of steam at 26 lbs. abso- 
lute, as compared with water at 39°, is 962. Now if 
the length of line R 26 be divided by this volume, and 
the quotient multiplied by each of the volumes of the 
other pressures represented at points 30, 35, 40, 45, 
etc., up to the initial pressure, the products will be 
the respective distances from the clearance line of 
points in the adiabatic curve. These points can be 
marked on the horizontal lines drawn from the 
clearance line to line R T. 

Starting with line R 26, it has been noted that its 
length is 3.0625 in., and that the volume was 962. 
3.0625 -^ 962 = .003. Then the volume of steam at 30 
lbs. is 841, which being multiplied by .003 = 2.5 in., the 
length of line 30. Next the volume at 35 lbs. = 728. 
Multiplying this volume by .003 = 2.1 in., length of 
line 35, and so in like manner for each of the other 
points. 

The process involves considerable figuring and care- 



254 ENGINEERING 

ful and accurate measurements, which should be made 
with a steel rule with decimal graduations. It is not 
expected that the cut Fig. 89 will be found accurate 
enough in its measurements to serve as a standard; it 
being intended only to serve as an illustration of the 
process. The diagram from which the illustration was 
drawn was taken from a 600 H. P. engine situated 
some 200 ft. from the boilers, and there was a con- 
siderable cooling of the steam by the time it reached 
the engine, the effect of which is apparent. The 
curve produced by the measurements is shown by the 
broken line. The process can be applied to any dia- 
gram. 

Power Calculations. The area of the piston (minus 
one-half the area of rod) multiplied by the M. E. P., as 
shown by the diagram, and this product multiplied by 
the number of feet traveled by the piston per minute 
(piston speed) wull give the number of foot pounds of 
work done by the engine each minute, and if this pro- 
duct be divided by 33,000, the quotient will be the 
indicated horse power (I. H. P.) developed by the 
engine. 

Therefore one of the first requisites in power calcu- 
lations is to ascertain the M. E. P. Beginning with 
the most simple, though only approximately correct, 
method of obtaining the average pressure, as illus- 
trated by Fig. 90, draw line A B touching at A and 
cutting the diagram in such manner that the space D 
above it will equal in area spaces C and E taken 
together, as nearly as can be estimated by the eye. 
Then with the scale measure the pressure along the 
line F G at the middle of the diagram, which will be 
c^he M. E. P. 

The process is based upon the theory that the 



DIAGRAM ANALYSIS 



255 



average width of any tapering figure is its width at 
the middle of its length. This method should not be 
relied upon as accurate, but is convenient at times 
when it is desired to make a rough estimate of the 
horse power of an engine. 

Figuring the M. E. P. by Ordinates. This is a very 
common method and one which can be relied upon to 
give accurate results, provided care is exercised in its 
use. 

The process consists in drawing any convenient 



FIGURE 90. 



number of vertical lines perpendicular to the atmos- 
pheric line across the face of the diagram, spacing 
them equally, with the exception of the two end 
spaces, which should be one-half the width of the 
others, for the reason that the ordinates stand for the 
centers of equal spaces, as for instance, line i, Fig. 91, 
stands for that portion of the diagram from the end to 
the middle of the space between it and line 2. Again, 
Mne 2 stands for the remaining half of the second 
space and the first half of the third, and so on. This 



25i) 



ENGINEERING 



is an important matter, and should be thoroughly under- 
stood, because if the spaces are all made of equal 
width, and measurements are taken on the ordinates, 
the results will be incorrect, especially in the case of 
high initial pressure and early cut off, following w^hich 
the steam undergoes great changes. 

If the spaces are all made equal, the measurements 
will require to be taken in the middle of them, and 
errors are liable to occur, whereas if spaced as before 
described, the measurements can be made on the 



ss 

to. I 
S 
7 




tJTjr. ns.p 



FIGURE 91. 






ordinates, which is much more convenient and will 
insure correct results. Any number of ordinates can 
be drawn, but ten is the most convenient and is amply 
sufficient, except in case the diagram is excessively 
long. For spacing the ordinates, dividers may be 
used, or a parallel ruler may be procured from the 
makers of the indicator; but one of the most con- 
venient and easily procurable instruments for this pur- 
pose is a common two-foot rule, and the method of 
using it is illustrated in Fig. 91. 

First draw vertical lines at each end of the diagram, 



DIAGRAM ANALYSIS 257 

perpendicular to the atmospheric line and extending 
downwards to the vacuum line, or below it if neces- 
sary, in order to have a point on which to lay the 
rule. In Fig. gi points A and B are found to be the 
most convenient. Now lay the rule diagonally across 
the diagram, touching at A and B, and the distance 
will be found to be 3^ in., or 60 sixteenths. 

Suppose it be desired to draw 10 ordinates. Divide 
60 by 10, which will give 6 sixteenths, or ^ in. as the 
width of the spaces, but as the two end spaces are to 
be one-half the width of the others, there will be ii 
spaces altogether, the two outer ones having a width 
equal to one-half of ^ or -^q. Now apply the rule 
ag'ain in the same manner, touching at points A and B, 
and with a sharp pointed pencil begin at A and mark 
the location of the first ordinate according to the rule, 
at a distance of y\ from the end. Then ^ from this 
mark make another one, which will locate the second 
ordinate, and proceed in like manner to locate the 
others. The last two or three marks generally come 
below the diagram, and if the diagram be taken from a 
condensing engine it may be necessary to tack it on to 
a larger sheet of paper in order to get these points. 
Having correctly located the ordinates, they may now 
be drawn perpendicular to the atmospheric line or 
vacuum line, either of which will answer. 

It should be noted that, owing to the diagonal posi- 
tion of the rule with relation to the atmospheric line, 
the spaces are not of the actual width as described by 
the rule, but this is unimportant, so long as they are of 
a uniform width. This method can be applied to any 
diagram, no matter what its length may be, and point 
B may be located at any distance below the atmos- 
pheric or vacuum lines, wherever it is the most con- 



258 ENGINEERING 

venient for the subdivisions on the rule, sixteenths, 
eighths, etc., so long as it is in line with the end of 
the diagram. Having thus drawn the ordinates, the 
M. E. P. may be found by measuring the pressure 
expressed by each one, using for this purpose the 
scale adapted to the spring used, adding all together 
and dividing by the number of ordinates which will 
give the average pressure. 

Referring to Fig. 91, begin with ordinate No. i on 
the diagram, from the head end of the cylinder. In 
this case a 40 spring was used. Lay the scale on the 
ordinate with the zero mark where it intersects the 
compression curve. The pressure is seen to be 49 lbs. 
Set this down at that end of the card and measure the 
pressure along ordinate No. 2, which is 55 lbs. Pro- 
ceed in this manner to measure all the ordinates, 
placing the resulting figures in a column, after which 
add them together and divide by 10. The result is 
26.71 lbs., which is the mean forward pressure (M. 
F. P.). To obtain the mean effective pressure, deduct 
the back pressure, which is represented by the distance 
of the exhaust line of the diagram above the atmos- 
pheric line in a non-condensing engine, and in a con- 
densing engine the back pressure is measured from the 
line of perfect vacuum, 14.7 lbs., according to the scale 
below the atmospheric line. 

In Fig. 91 the back pressure is found to be 3 lbs. 
Therefore the M. E. P. of the head end will be 
26.71 - 3 = 23.71 lbs. On the crank end the M. F. P. 
is 27.23 lbs, and 27.23 - 3 = 24.23 lbs. = M. E. P. The 
average effective pressure on the piston, therefore, wil' 
be 23.71 + 24.23 -;- 2 = 23.97 lbs. 

Unless great care is exercised in the measurements, 
errors are liable to occur in applying this method, 



DIAGRAM ANALYSIS 259 

especially with scales representing high pressures, as 
60, 80, etc. The most convenient and reliable method 
is to take a narrow strip of paper of sufficient length, 
and starting at one end, apply its edge to each ordinate 
in succession and mark their lengths on it consecu- 
tively with the point of a knife blade or a sharp pen- 
cil. Having thus marked on the paper the total length 
of all the ordinates, ascertain the number of inches and 
fractions of an inch thereon, the fractions to be 
expressed decimally, and divide by the number of 
ordinates. The quotient will be the average height of 
the diagram, and as the scale expresses the number of 
pounds pressure for each inch or fraction of an inch in 
height, if the average height of the diagram be multi- 
plied by the number of the scale, the product will be 
the M. F. P. 

Referring again to Fig. 91, if the lengths of the 
ordinates drawn on the head end diagram be measured, 
their sum will be found to be 6y^2 or 6.666 in. Divid- 
ing this by 10 gives .666 in. as the average height. 
The mean forward pressure will then be as follows: 
.666 X 40 = 26.64 lbs., or oractically the same as found 
by the other method. 

Fig. 92 illustrates a type of diagram frequently met 
with, and one which requires somewhat different 
treatment in estimating the power developed. It will 
be noticed that, owing to light load and early cut off, 
the expansion curve drops considerably below the 
atmospheric line, notwithstanding that the engine 
from which this diagram was taken is a non-con- 
densing engine. When release occurs at R, and the 
exhaust side of the piston is exposed to the atmos- 
phere, the pressure immediately rises to a point equal 
to, or slightly above, that of the atmosphere. 



^60 



ENGINEERING 



Fig. 92 was taken during a series of experiments 
made by the author for the purpose of ascertaining the 
friction of shafting and machinery, and the engine it 
was obtained from is a Buckeye 24 x 48 in. The 
boiler pressure at the time was only 40 lbs., and a No. 
20 spring was used. The ordinates are drawn accord- 
ing to the method illustrated in Fig. 91. By placing 
the rule on points A and B, the distance between 
those two points is found to be 3^ in., or 58 sixteenths. 
Dividing this by 10 gives 5.8 sixteenths, or nearly s/^ 







FIGURE 92. 



in., as the width of the spaces; the two end spaces 
.teing one-half of this, or y\ in. wide. The first five 
©rdinates, counting from A, express forward pressure, 
represented by the arrows. The remaining five ordi- 
nates, counting from B, express counter or back pres- 
sure, represented by the arrows pointing in the 
opposite direction. Measuring the pressures along 
the first five ordinates, and adding them together, 
gives 63.1 lbs., which divided by 5 gives 12.65 lbs. as 
the mean forward pressure (M. F. P.). 



DIAGRAM ANALYSIS 



261 



Then figuring up the counter pressure in the same 
manner on the other five ordinates, beginning at B, 




COFFIN AVERAGER OR PLANIMETER, 

the result is 4.25 lbs. The M. E. P. therefore will be 
12.65 -4.25 = 8.4 lbs. 

Obtaining the M. E. P. with the Planimeter. The area 
of the diagram represents the actual work done by the 



262 ENGINEERING 

Steam acting upon the piston. In a non-condensing 
engine the lower or exhaust line of the diagram must 
be either coincident with or slightly above the atmos- 
pheric line in order to express positive work. Any 
deviation of this line, either above or below the atmos- 
pheric line, represents counter pressure, the amount of 
which may be ascertained by measurements with the 
scale, and should be deducted from the mean forward 
pressure. 

On the other hand, the exhaust line of a diagram 
from a condensing engine falls more or less below the 
atmospheric line, according to the degree of vacuum 
maintained, and the nearer this line approaches the 
line of perfect vacuum, as drawn by the scale, 14.7 lbs. 
below the atmospheric line, the less will be the counter 
pressure, which in this case is expressed by the dis- 
tance the exhaust line is above that of perfect vacuum. 

The prime requisite therefore in making power cal- 
culations from indicator diagrams is to obtain the 
average height or width of the diagram, supposing it 
were reduced to a plain parallelogram instead of the 
irregular figure which it is. 

The planimeter, Fig. 93, is an instrument which will 
accurately measure the area of any plane surface, no 
matter how irregular the outline or boundary line is, 
and it is particularly adapted for measuring the areas 
of indicator diagrams, and in cases where there are 
many diagrams to work up, it is a very convenient 
instrument and saves much time and mental effort. In 
fact, the planimeter has of late years become an almost 
indispensable adjunct of the indicator. It shows at 
once the area of the diagram in square inches and 
decimal fractions of a square inch, and when the area 
is thus known it is an easy matter to obtain the aver- 



DIAGRAM ANALYSIS 



263 



age height by simply dividing the area in inches by 
the length of the diagram in inches. Having ascer- 
tained the average height of the diagram in inches or 
fractions of an inch the mean or average pressure is 
found by multiplying the height by the scale. Or the 
process may be made still more simple by first multi- 
plying the area, as shown by the planimeter in square 




inches and decimals of an inch, by the scale, and 
dividing the product by the length of the diagram in 
inches. The result will be the same as before, and 
troublesome fractions will be avoided. 

Questions 
I. What advantage is gained by placing the valves 
of a Corliss engine in the cylinder head? 



264 .ilNGINEERING 

2. What two important factors must be considereoi 
in calculating the steam consumption of an engine? 

3. What advantage, in an economical way, is gamed 
by compression? 

4. How is the piston displacement of an engine 
ascertained? 

5. How is the steam consumption per horse power 
per hour calculated? (See Figs. 79 and 80.) 

6. What effect does compression have upon the work 
area of an indicator diagram? (See Fig. 80.) 

7. How can the steam consumption, as shown by 
the diagram, be corrected for clearance and compres- 
sion? (See Figs. 81, 82 and 83.) 

8. What do the expansion and compression curves 
of a diagram show? (See theoretical clearance.) 

g. If the clearance of an engine is not known, how 
may it be determined theoretically from an indicator 
diagram? (See Figs. 84 and 85.) 

10. What other method may be employed to ascer- 
tain the clearance? 

11. What is Boyle's law for gases? 

12. Is steam a gas? 

13. What is a hyperbolic curve? (See Fig. 86.) 

14. How may a theoretical curve be constructed 
from an indicator diagram? (See Fig. 87.) 

15. What effect does reevaporation have upon the 
expansion curve? 

16. When does reevaporation take place within the 
cylinder? 

17. How does a leaky steam valve affect the ter- 
minal pressure? 

18. If the piston rings leak, what is the result? 

19. What is an adiabatic curve, and what conditions 
are necessary in order to produce it? 



DIAGRAM ANALYSIS 265 

20. What IS the rule for computing the horse power 
developed by an engine? 

21. What important factor is necessary in all power 
calculations? 

22. How may the M. E. P. be found? (See Figs. 
91 and 92.) 

23. What does the area of the diagram represent? 

24. In a diagram from a non-condensing engine, 
where sTiould the exhaust line be? 

25. If the exhaust line of a diagram is above the 
atmospheric line, what does it show? 

26. Where should the exhaust line of a diagram from 
a condensing engine be? 

27. How is the M. E. P. ascertained by the plani- 
meter? 



CHAPTER XI 

ENGINE OPERATION 

Engine operation — Simple engines — Compound engines — Con- 
densing and non-condensing engines — Condensers — Surface 
and jet condensers — Starting a condensing engine — Rules for 
estimating quantity of condensing water required — The gov- 
ernor — Speed regulation — How to keep a governor in good 
working condition — Lubrication of an engine — Running 
"over" or "under" — Oiling the bottom guide on horizontal 
engines — Oiling the crank pin and main bearings — Shaft gov- 
ernors—Keying up an engine — What to do with a hot pillow 
block — Feed water heaters — Economy of using exhaust steam 
for heating feed water — Changing the speed of an engine. 

The following general suggestions regarding the 
operation of engines are made with the object in view 




CROSS COMPOUND DIRECT CONNECTED CORLISS ENGINE, ALLI? 
CHALMERS CO. 



of assisting young engineers or those whose experience 
has been limited to one or two types of engines. 

In many cases a young man starts in as a fireman in 

266 



ENGINE OPERATION 267 

a certain plant, and by industry and a strict devotion 
to duty becomes able in course of time to handle not 
only the boilers successfully, but is at times required 
to run the engine in the absence of the engineer. He 
thus acquires the ability to operate that particular 
engine, while at the same time he may be compar- 
atively ignorant of the peculiarities of other types. 
Or an engineer may have had years of experience with 
simple non-condensing engines, but if called upon to 
operate a compound condensing engine, he would find 
that he had a great deal to learn. 




TANDEM COMPOUND ENGINE, BUCKEYE ENGINE CO. 

Engines may be divided into two general classes, 
viz., simple and compound. 

A simple engine may be either condensing or non- 
condensing, but its leading characteristic is, that the 
steam is used in but one cylinder, and from thence it is 
exhausted either into the atmosphere or into a con- 
denser. 

A compound engine is one in which the steam is 
made to do work in two or more cylinders before it is 
allowed to exhaust, and this class of engine may be 
either condensing or non-condensing. 



•268 



ENGINEERING 




ENGINE OPERATION 



269 



In a non-condensing engine the pressure of the 
atmosphere, amounting to 14.7 lbs. per square inch at 
sea level, is constantly in resistance to the motion of 




KNOWLES JET CONDENSER. 



the piston. Therefore the exhaust pressure cannot 
fall below the atmospheric pressure, and is generally 
from two to five pounds above it, caused by the resist- 
ance of bends and turns in the exhaust pipe, or other 



270 ENidHNEERING 

causes which tend to retard the free passage of the 
steam. 

The advantage, from an economical point of view, 
of exhausting the steam into a condenser in which a 
vacuum is maintained, is fully set forth in Chapter 
VIII. on Definitions. (See Vacuum.) 

Condensers are of two classes, viz., jet condensers 
and surface condensers. 

In a jet condenser the steam is exhausted into an 
air-tight iron vessel of any convenient shape, gener- 
ally cylindrical and of suitable size, and is there con- 
densed by coming in contact with a jet of cold water, 
admitted in the form of a spray. The air pump, which 
also maintains a vacuum in the condenser, draws this 
water, together with the condensed steam, away from 
the condenser. 

The surface condenser, like the jet condenser, con- 
sists of an air-tight iron vessel, either cylindrical or 
rectangular in shape, but unlike the jet condenser, it 
is fitted with a large number of brass or copper tubes 
of small diameter, through which cold water is forced 
by a pump, called a circulating pump. A vacuum is 
also maintained in the body of the condenser by the 
air pump, and the steam exhausting into this is con- 
densed by coming in contact with the cool surface of 
the tubes. Or, as is often the case, the exhaust steam 
passes through the tubes in place of around them, and 
the condensing water is forced into and through the 
body of the condenser, the vacuum in this case being 
maintained in the tubes. Owing to the fact that in a 
surface condenser the steam does not mix with the 
water, a larger quantity of condensing water is required 
than in a jet condenser, but on the other hand, an 
advantage is gained by having the pure water of con- 



ENGINE OPERATION 271 

densation; in other words, the condensed steam, which 
may be returned to the boilers along with the regular 
feed water supply, and will greatly aid in preventing 
the formation of scale, while the water of condensation 
as it comes from a jet condenser, being mixed with 
oil and other impurities, is not, as a rule, suitable to 
be fed to boilers. 

There are many different types of jet condensing 




WORTHINGTON SURFACE CONDENSER, WITH AIR AND CIRCU- 
LATING PUMP. 



apparatus, in some of which no air pump is used; theil 
action being based somewhat upon the principle of the 
injection used for feeding boilers. In this type of jet 
condenser the supply of condensing water is drawn fron? 
outside pressure, either from an overhead tank or other 
source, and passing into an annular enlargement of the 
exhaust pipe, is discharged downwards in the form or 
a cylindrical sheet of water into a nozzle which gradu- 
ally contracts. The exhaust steam, entering at th^ 



272 



ENGINEERING 



same time, is condensed, and the contracting neck oi 
the cone shaped nozzle gradually brings the water to a 
solid jet, and it rushes through the nozzle with a veloc- 
ity sufficient to create a vacuum. This type of con- 
denser can only be used where the discharge pipe has 
a free outlet. 

The jet condenser with air pump attached is the 
most reliable as well as econom- 
ical for general purposes, for the 
reason that with this type the sup- 
ply of condensing water may be 
drawn from a well or other source 
lower than the level of the con- 
denser. These condensers are also 
generally fitted with a * 'force in- 
"ection," as it is called, which is 
simply a connection between the 
condenser and water main or tank, 
for the purpose of letting cold water 
into the condenser to condense the 
exhaust steam when starting the 
engine, and thus aid in forming a 
vacuum. When a good vacuum has 
been established and the engine is 
running up to speed, the force injection may be shut 
off, and the water will flow into the condenser from 
the well by suction. The above refers to engines in 
which the air pump receives its motion directly from 
the engine. 

Another type of jet condensing apparatus is the 
independent air pump and condenser, which is still 
better, for the reason that the air pump, which is sim- 
ply an ordinary double acting steam pump, may be 
started independently of the engine, and, in fact, 




SIPHON CONDENSER. 



ENGINE OPERATION 273 

before the engine is started, thus creating a vacuum in 
the condenser, and greatly facilitating the starting of 
the engine. Another great advantage in the inde- 
pendent condensing apparatus is that there is not so 
much danger of the water backing up into the cylinder 
in case of a sudden shut down of the engine, because 
the air pump may be kept in operation, thus relieving 
the condenser of water; whereas, if the air pump gets 
its motion from the engine, it will of course stop'when 
the engine stops, and unless the injection water is shut 
off immediately after closing the throttle there is 
great danger of the cylinder becoming flooded with 
water, resulting very often in a broken cylinder head, 
or a bent piston rod. 

The quantity of water required to condense the 
exhaust steam of an engine is determined by three 
factors: First, the density, temperature and volume of 
the steam to be condensed in a given time; second, 
the temperature of the overflow or discharge, and 
third, the temperature of the injection water. For 
instance, the temperature of the injection water may 
be 35° in the winter and 70° in the summer. Or it 
may be desired to keep the overflow at as high a tem- 
perature as possible for the purpose of feeding the 
boilers. Again, the pressure, and consequently the 
temperature of the exhaust steam as it enters the con- 
denser, varies witn different engines, and often with 
the same engine, according as the load is light or 
heavy. Therefore the only accurate method of esti- 
mating the amount of condensing water required per 
minute or per hour, under any and all conditions, is to 
first ascertain the weight of water required to con- 
dense one pound weight of steam at the temperature 
and pressure at which the steam is being exhausted 



274 ENGINEERING 

In these calculations the total heat in the steam must 
be considered. This means not only the sensible heat, 
but the latent heat also. 

The formula for solving the above problem may be 

H — T 

expressed as follows: ^^ — =r = W, in which 

H = total heat in the steam, 
T = temperature of the overflow, 
I = temperature of the injection water, 

W = weight of water required to condense one pound 
weight of steam. 

To illustrate, suppose the absolute pressure of the 
exhaust, as shown by the indicator diagram, is 7 lbs. 
Referring to Table 5, it will be seen that the total heat 
in steam at 7 lbs. absolute is 1 135.9 heat units. 
Assume the temperature of the overflow to be 110°, 
which is as high as is consistent with a good vacuum 
Now the total heat to be absorbed from each pound 
weight of steam in this case would be 1135.9—110 = 
1025.9 B. T. U. 

Suppose the temperature of the condensing water to 
be 55° and the temperature of the overflow being 110°, 
there will be 110° — 55° = 55° of heat absorbed by each 
pound of water passing into and through the con- 
denser, and the number of pounds of water required to 
condense one pound weight of steam under the above 
conditions will equal the number of times 55 is con- 
tained in 1025.9. Expressed in plain figures the cal- 
culation is iif^^£5^= 18.65 lbs. 

In order to ascertain the quantity of condensing 
water required per horse power per hour, it is only 
necessary to know the number of pounds weight of 
steam consumed by the engine per horse power per 
hour, as shown by the indicator diagram, and multiply 



ENGINE OPERATION 275 

this by tho weight of condensing water required per 
pound of steam, as found by the above solution. 

Thus, suppose the steam consumption of the engine 
to be 17 lbs. per I. H. P. per hour. Then 17 x 18.65 
= 317.05 lbs. per hour, which reduced to gallons = 38.2 
gals. 

Or, if the steam consumption is not known, and the 
weight only of condensing water required per hour is 
desired, regardless of the horse power developed by 
the engine, it will be necessary, first, to estimate the 
total volume of steam exhausted per hour and calcu- 
late its weight from its known pressure. 

Thus, assume the engine to be 24x48 in., and the 
R. P. M. to be 80. Then the piston displacement will 
equal area of piston less one-half area of rod multi- 
plied by length of stroke. Referring to Table 9, the 
area of a circle 24 in. in diameter = 452.39 sq. in 
Suppose the piston rod to be 4.5 in. in diameter, its 
area, according to Table 9, is 15.904 sq. in., one-half 
of which = 7.952 sq. in. The effective area of the pis- 
ton now becomes 452.39 — 7.952 = 444.43 sq. in., and 
the piston displacement equals 444.43 x 48 = 21332.64 
cu. in. Dividing this by 1728 (number of cubic inches 
in a cubic foot) gives 12.34 cu. ft. of piston displace 
ment. The total volume of steam exhausted per min- 
ute, therefore, will be 12.34 x 2 x 80 = 1974.4 cu. ft. 

The absolute pressure of the exhaust may again be 
assumed to be 7 lbs. per square inch. Referring to 
Table 5, the weight of one cubic foot of steam at 7 
lbs. absolute is .0189 lbs., and the total weight of steam 
exhausted per minute, therefore, would be 1974.4 x 
.0189 = 37.3 lbs., and if 18.65 lbs. water is required to 
condense one pound of steam, the quantity required 
per minute would be 37.3 x 18.65 =695.8 lbs., or per 



376 



ENGINEERING 



hour, 41748 lbs., equal to 5029 gals. This is at the rate of 
8.7 lbs., or a little more than one gallon per revolution for 
a 24X48 in. simple condensing engine. 

The Governor. The proper regulation of speed is a 
very important point in the operation of engines, and 
in order to attain this most desirable object, due atten- 
tion must be paid to the governor. 
If it be a throttling governor (see 
Cliapter VIII, on Definitions), care 
should be taken to not pack the 
small valve stem too tight, nor allow 
the packing to become hard from 
long usage. The packing nuts should 
be left loose enough to allow a 
slight leakage of steam past the 
stem. This will keep it lubricated 
and the slightest variation of the 
governor balls will be transmitted 
to the valve, and the speed will be 
regular. 

If the engine has an automatic 
cut ofif mechanism actuated by a fly 
ball governor, it is obvious that all 
the moving parts of the governor 
should work with as little friction as possible. Good 
oil and enough of it should be used. Particular atten- 
tion should be paid to the dash pot connected with the 
governor, the object of which is to regulate the varia- 
tions of the governor and prevent a jerky movement. 
It often happens, especially with new engines, that 
the small piston in the dash pot fits too snug, and the 
consequence is that it sticks ; causing the governor to 
be slow in responding to changes in the speed of the 
engine. 




PICKERING HORI- 
ZONTAL GOVERNOR. 



ENGINE OPERATION 



277 



It is a good plan sometimes to take the dash pot pis- 
ton out, and putting it in a lathe, reduce its diameter 
slightly, and also round off the sharp edges. The oil 
used in the dash pot should not be allowed to become 
gummy by being used too long without changing it for 
fresh oil. 

Lubrication. The proper lubrication of all the work- 
ing parts of an engine is a matter of prime importance, 




DOUBLE CONNECTION LUBRICATOR. 



not only in prolonging the life of the engine, but in 
reducing friction, and thus increasing efficiency. 
Various types of lubricators have been devised for 
introducing oil into the valve chest and cylinder, but 
probably the most reliable and easily managed appa- 
ratus for this purpose is a good oil pump worked by 
the engine itself, for the reason that it is positive and 
the flow of oil is not easily affected by changes in 



278 



ENGINEERING 



temperature. In the case of large horizontal engines 
especially, it is good practice to introduce a little 
graphite along with the cylinder oil once or twice a 
day. 

In many cases trouble is experienced with the bot- 




<^^^<«fr 



FIGURE 94. 



torn guides of horizontal engines, especially if the 
engine ''runs over," as illustrated by Figs. 94 and 95, 
where it will be seen that in addition to the weight of 
the crosshead, the thrust or pressure consequent upon 
the pull, Fig. 94, and push. Fig. 95, also comes upon 
the bottom guide both with the inward and outward 




FIGURE 95. 



Strokes; whereas with an engine ''running under,** the 
thrust is just in the opposite direction, and the pres- 
sure comes upon the top guide. 

The best method of lubricating the lower guide of a 
horizontal engine is to drill through from the under- 



ENGINE OPERATION 



279 



side at a point near the center of the guide, and con- 
nect a small size pipe, ^ or ^ in., to which an oil or 
grease cup can be attached. The oil thus forced up 
from beneath will serve a much better purpose than if 
dropped on the guide, to be instantly scraped off by 
the crosshead. 

One of the best devices for oiling the crank pin is 
the center oiler, illustrated in Fig. 96. An oil hole is 
drilled along the center line of the pin to a point about 
midway of its length, and another hole from the 




FIGURE 96. 



wearing surface of the pin at right angles to the first 
hole. The two holes meet at the center of the pin 
and form a route by which the oil is conducted to the 
point where it is most needed. The hole at the outer 
end of the pin is enlarged and threaded to receive the* 
oil pipe, one end of which is connected to the pin by 
means of a short nipple and elbow, while the other 
end is in line with the center of the main shaft and 
remains in that position while the crank revolves. 
The oil is fed into this end of the pipe through an 



280 ENGINEERING 

elbow or hollow ball screwed to the end of the pipe, 
and the supply may be regulated at will by the engi- 
neer, as the cup is at all times under his control. 

The pillow block or main bearing of an engine 
demands and should receive the most careful attention 
from the engineer, for the reason that there is where 
the greatest friction occurs, and if neglected for even 
a short time, trouble will occur. 

The main bearings of most engines are fitted with 
apparatus for oiling them by which the oil is dropped 
upon the top of the journal, when in fact the place that 
the oil is most needed is at the bottom or underside of 
the bearing. In horizontal engines, especially, there is 
a constant pressure on the bottom of the bearing, due 
to the weight of the flywheel and main shaft, and this 
pressure prevents the greater part of the oil, if fed in 
on top, from reaching the lower surface. Therefore 
the lubrication of pillow blocks may be greatly facil- 
itated by connecting, whenever it is possible to do so, 
at least one oil pipe in such a way that it will conduct 
the oil to the bottom of the bearing. In case a pillow 
block or other bearing shows signs of warming up, 
good results may often be obtained by using from 25 
to 50 per cent, of cylinder oil m.ixed with the regular 
engine oil. 

.Every engineer should establish a regular system of 
oilmg his engine, as for instance, by having regular 
intervals of time for going around the engine and 
inspecting all the working- parts. A good rule is to 
make the rounds about every twenty minutes. In this 
way no part will be neglected, and the danger of 
having hot bearings or of other accidents happening 
will be greatly lessened. 

Many automatic cut off engines, especially those of 



ENGINE OPERATION 281 

the high speed type, are fitted with isochronal or shaft 
governors. There are various styles of these gov- 
ernors, but all or nearly all of them control the admis- 
sion of steam to the cylinder, and consequently the 
point of cut off by varying the angular advance of the 
eccentric, which in such engines is free to move across 
the shaft, being entirely under the control of the 
governor. 

Very close regulation is generally obtained by the 




ISOCHRONAL OR SHAFT GOVERNOR, BUCKEYE ENGINE CO. 

use of shaft governors, but particular attention should 
be given to the lubrication of the steam valve, which, 
with this class of engines, is generally a slide valve of 
some description, and although it may be ever so 
nicely balanced, yet if it does not get sufficient oil, the 
friction due to dry surfaces rubbing together, will put 
extra work on the governor, and the speed is liable to 
be irregular. 

Keying Up. To keep the working parts of an engine 
properly keyed up so as to take up the lost motion 



282 ENGINEERING 

without causing the bearings to heat, is one of the 
most delicate and exacting duties of the engineer. 
Every engineer worthy of the name should aim to have 
a smooth and quietly running engine. In fact, this 
is one of the principal tests of his skill as an engineer. 

A few general suggestions may be given here, but 
much more depends upon the good judgment of the 
engineer himself. 

In connecting up an engine, as for instance, the 
crank pin and crosshead, the key should first be driven 
in until it is solid, that is, until the brasses clamp the 
pin tightly. Then place a small ruler across the face 
of the gib and key, and with the point of a knife blade, 
or a steel scriber, make a fine mark along the edge of 
the ruler. This will be the "solid mark.'' Now back 
the key up by light blows with the hammer, which 
should be of copper, until the brasses are just loose 
enough on the pin to permit a side movement of the 
rod. If the rod is very heavy, hold a block of wood 
against the side of the rod near the pin and give it a 
blow with a sledge. If there is no movement, back 
the key a little more, and keep trying until there is a 
side movement. There should be a space of at least 
^^ in. between the sides of the brasses and the flange 
of the pin, so as to allow a slight side play. If it is 
found, after running a while, that there is too much 
lost motion, causmg the engine to pound, put the ruler 
across the gib and key again, and with a lead pencil 
draw a line. Then loosen the set screw and drive the 
key in a distance equal to the width of the line, and 
no more. This process should be repeated at intervals 
until the pound is all gone, or the bearing begins to 
warm up slightly, indicating that the brasses are up as 
close as they will run. 



ENGINE OPERATION 283 

The adjustment of pillow blocks also requires a large 
measure of skill and good judgment, and should be 
done by degrees; but when once adjusted properly and 
kept well oiled, the matter of keeping them in good 
working condition becomes greatly simplified. 

If a pillow block, or other bearing filled with babbit 
metal, should become heated to such a temperature as 
to cause the metal to run, do not shut down the engine 
at once and turn on a stream of cold water, because 
this will only make matters worse, causing the metal 
to stick to the journal, and the labor and trouble of 
cleaning it out will be increased. The best method to 
pursue in such an emergency is to gradually slow the 
engine down and keep it moving at as slow a speed as 
it will run, and in the meantime a small stream of 
cold water may be allowed to flow over the bearing, 
applying it to all parts as nearly as possible until it is 
cooled, after which the engine may be stopped and 
repairs made. 

Heating Feed Water. Every steam plant should be 
provided with one or more heaters for the purpose of 
utilizing the exhaust steam for heating the feed water, 
and the exhaust, not only of the engine, but of the 
feed pumps and all other steam pumps connected with 
the plant, should be led into it if possible. This 
applies especially to non-condensing engines, and 
even if the engine be a condensing engine the exhaust 
may be passed through a closed heater before going 
into the condenser. 

The percentage of saving in heat effected by heating 
the feed water with exhaust steam which would other- 
wise go to waste, may be ascertained by the following 
rule: 

Multiply the difference in the total heat in the 



284 ENGINEERING 

water above 32°, before and after heating, by 100, and 
divide the product by the total heat required to con- 
vert the water into steam from the initial temperature. 
The quotient will be the per cent, of saving. 

The following example will serve to illustrate the 
process: Suppose the initial temperature of the water 
to be 50"^, and that by means of the heater its tem- 
perature is increased to 183° before entering the 
boiler. The steam pressure being 100 lbs. gauge, or 
115 lbs. absolute. By referring to Table 5, it will be 
seen that 

Water at 182.9"^ temp, contains 151.5 heat units, 

The difference = 133.5 ^^^^ units. 

One pound of steam at 115 lbs. absolute pressure 
contains above 32°, 1,185 ^^^^ units, and for each 
pound of water, at 50^, converted into steam at the 
above pressure, there would be required 1,185 — 18- 
1167 heat units; but 133.5 heat units having been 
added to the water while passing through the heater, 
the problem now becomes '^^5^^— =11.44 per cent., 
saving in heat. 

Two classes of heaters are available for this purpose, 
viz., open heaters and closed heaters. 

In the open heater the exhaust steam comes in con- 
tact with and mingles with the water, and a portion of 
it is condensed and returns to the boiler. In this 
respect the open heater has an advantage over the 
closed type, in which the water is kept separate from 
the exhaust steam by passing it through tubes that are 
surrounded by the steam which is confined in the outer 
shell of the heater. In some types of the closed heater 
the steam passes through the tubes, which are in turn 



ENGINE OPERATION 



285 



STEAm 



surrounded by the water. A heater of either class 
should be sufificiently large to allow the water to pass 
through it slowly, in order that it may absorb all the 
heat possible. About one-third of a square foot of 
heating surface should be allowed per horse power for 
a closed heater, and it should have sufficient volume 
to contain water enough to supply the boilers for a 
quarter of an hour. If a heater is too small for the 
engine it is liable to cause 
back pressure on the ex- 
haust. 

There is no saving in 
heat, but rather a loss in 
using live steam to heat 
the feed water, but on the 
other hand, if the water is 
bad, it can be purified to a 
certain extent by passing 
it through a live steam 
heater on its way to the 
boiler. 

Probably the most eco- 
nomical device for feed- 
ing boilers is the exhaust 
injector, which not only 
feeds the boiler, but utilizes all the available heat in the 
exhaust steam and returns it to the boiler. The diffi- 
culties attending the use of the exhaust injector are 
that it cannot force water against a pressure above 75 
or 80 lbs., and that it will not lift its water supply by 
suction. 

The principle by which an injector is able to force 
water against a higher pressure than that of the steam 
by which it is operated, lies In the fact that the mix- 




SECTIONAL VIEW OF PEN- 
BERTHY INJECTOR. 



286 ENGINEERING 

ture of water and steam rushes with such velocity into 
the vacuum formed by the condensation of the steam, 
that the momentum thus acquired carries it into the 
boiler against the higher pressure. 

Live steam injectors, while being much less econom- 
ical than the steam pump with heater, are, neverthe- 
less, a valuable adjunct of a steam plant. They are 
lifting and non-lifting. A lifting injector in good con- 
dition, with no air leaks in the suction pipe, will raise 
the water by suction about 20 ft. With the non-lifting 
injector the water supply must flow into the injector, 
and it may be handled at a temperature as high as 
150°, although not so reliable as at lower temperatures. 

A good free working check valve and one that will 
not leak, is one of the most important requisites in the 
feeding of boilers, and especially is this the case when 
an injector is used. 

Sometimes an injector is prevented from working by 
dirt being drawn in through the suction pipe. This 
trouble can be avoided by fitting the pipe with a 
strainer. If the tubes become clogged with scale, they 
should be soaked in a dilute solution of muriatic acid, 
say one part of acid to ten parts of water. All t!.c 
joints and connections should be air tight, and the 
valves should be properly packed, otherwise the 
injector will be a constant source of trouble. 

Changing the Speed of an Engine. It sometimes hap- 
pens that it is desired to permanently change the speed 
of an engine, and the method of doing this is as fol- 
lows : 

If it is desired to increase the speed but two or three 
revolutions, it can generally be accomplished by mov- 
ing the counter balance (which most governors have) 
farther out on the lever, although there is a limit to 



ENGINE OPERATION 287 

this, because if moved too far, either in, to decrease 
the speed, or out to increase tne speed, the effect will be 
to destroy the true action of the governor, and its move- 
ments will be jerky. The location of the counter bal- 
ance should be at that point where the governor works 
the best at the speed at which it was designed to run, 
and which is generally marked on the governor. And 
this can only be determined by much patient experi- 
menting on the part of the engineer. If moving the 
counter balance does not bring about the desired 
increase of speed, the next move is to increase the 
diameter of the governor pulley so that the propor- 
tions of the pulleys on the engine shaft and the gov- 
ernor will be such that the governor will continue to 
run at its normal speed, while the speed of the engine 
has been increased the desired number of revolu- 
tions. 

To illustrate, assume the engine to be making 75 
revolutions per minute, and that the pulley on the 
engine shaft, upon which the governor belt runs, 
is 12 in. in diameter, and that the governor pulley is ? 
in. in diameter. 

Suppose it is desired to increase the speed of th.. 
engine to 85 revolutions per minute. First find the 
speed of the governor with the engine running at 75 
revolutions. 

The formula is, 
Speed of engine x diameter of shaft pulley , 

Diameter of governor pulley ^ 

governor. Thus, '^^^^^ = 112. 5, revolutions for gov- 
ernor. 

Next find what the diameter of the governor pulley 
must be to allow the governor to still run at 112. 5 revo- 
/utions while the engine runs at 85 revolutions. 



288 ENGINEERING 

The formula is, 

Speed of engine x diameter of shaft pulley ,. 

-^ ?5; J — 7 ~ = diameter 

Speed ot governor 

of governor pulley. Thus, ?f^ = 9.06 in., diameter 

of new pulley required for governor. 

Should it be desired to decrease the speed of the 

engine, the same rules and formula will apply for 

ascertaining the diameter of the governor pulley, which 

in this case would have to be reduced in size. 



Questions 

1. Into what two general classes may engines be 
divided? 

2. In what respect do they differ? 

3. What advantage has a compound engine over a 
simple engine? 

4. What advantage economically has a condensing 
engine over a non-condensing engine? 

5. How many kinds of condensers are there? 

6. Describe a jet condenser. 

7. Describe a surface condenser. 

8. Is an air pump absolutely necessary with all jet 
condensers? 

9. What is meant by an independent air pump and 
condenser? 

10. What three factors determine the quantity of 
condensing water required by an engine? 

11. What is the rule for ascertaining the quantity of 
condensing water required by an engine? 

12. How may the quantity of condensing water 
required per horse power per hour be ascertained? 

13. What precautions should be observed with a 
throttling governor? 



ENGINE OPERATION 289 

14. What general rules should be followed in the 
operation of an automatic cut off governor? 

15. What is the most reliable device for introducing 
oil into the valve chest and cylinder? 

16. How may the bottom guide of a horizontal 
engine be best lubricated? 

17. What reliable device may be used in the lubri- 
cation of the crank pin? 

18. What precautions should be observed in the 
lubrication of the main bearings or pillow blocks? 

19. What should be done with a pillow block that 
shows signs of warming up? 

20. How does an isochronal, or shaft governor, regu- 
late the speed of an engine? 

21. How is the shaft governor affected if the steam 
valve is not properly lubricated? 

22. Describe the proper method of keying up an 
engine. 

23. What should be done in case a main bearing 
becomes heated sufificiently to melt the babbitt? 

24. How may the exhaust be utilized to an advan- 
tage? 

25. What is the rule for ascertaining the percentage 
of saving in heat when an exhaust heater is used? 

26. What two classes of heaters are available? 
2j, What is an open heater? 

28. Describe a closed heater. 

29. Is there a saving in heat effected by using a live 
steam heater? 

30. What advantage then is derived from its use? 

31. Upon what principle does an injector work? 

32. Into what two types are injectors divided? 

33. What particular valve in the feed pipe of a boiler 
should always be kept in good condition? 



290 ENGINEERING 

34. How may an injector that has become clogged 
with dirt or scale be cleaned? 

35. What precautions should be observed in fitting 
up an injector? 

36. How may the speed of an engine be slightly 
increased? 

37. If it is desired to increase the speed consider- 
ably, how may it be done? 

38. If it is desired to decrease the speed, what 
changes are necessary? 



Engineering 

PART II 

CHAPTER I 
THE BOILER 

Importance of correct knowledge of the construction and 
strength of steam boilers — Tensile strength of steel boiler 
plates — Dr. Thurston's specifications — Specifications of U. S. 
board of inspectors of steam vessels — Punched and drilled 
plates — Rivets and rivet iron and steel — Efficiency of the 
joints — Proportions of double riveted butt joints — Lloyd's 
rules for thickness of plate and diameter of rivets — Cor- 
rect design of triple riveted butt joints — Calculations for 
efficiency of different forms of joints — Discussion of various 
ways in which failure may occur in different styles of joints 
— Necessity for higher efficiencies in riveted joints — Quad- 
ruple and quintuple butt joints— Staying flat surfaces — 
Different methods of staying a boiler — Correctly designed 
stays — Stay bolts for fire box boilers — The Belpaire boiler — 
Vanderbilt Locomotive with Morison fire box — Gusset stays — 
Through stay rods — Calculating strength of stayed surfaces — 
Area of segments — Proper spacing of stays — Strength of un- 
stayed surfaces — Dished heads — Welded seams. 

As it is of the highest importance, not only to the 
engineer in charge of the plant, but also to his assist- 
ants, and in fact to all persons whose business com- 
pels them to be in the vicinity of the boiler-room, that 
there should be absolutely no doubt as to the safe 
construction of the boilers and their ability to with- 
stand the pressures under which they are operated, the 

295 



296 ENGINEERING 

author has compiled the following additional data 
regarding the construction and strength of boilers. 
The deductions and reports of tests and experiments 
made by such eminent authorities as Dr. Thurston, 
Prof. Wm. Kent, Dr. Peabody, D. K. Clark, Hutton 
and many other experts have been consulted, and the 
author has also added the results of his own obser- 
vations, collected during an experience of thirty-five 
years as a practical engineer. 

When steel was first introduced as a material for 
boiler plate, it was customary to demand a high tensile 
strength, 70,000 to 74,000 lbs. persq. in., but experience 
and practice demonstrated in course of time that it 
was much safer to use a material of lower tensile 
strength. It was found that with steel boiler plate of 
high tenacity there was great liability of its cracking, 
and also of certain changes occurring in its physical 
properties, brought about by the variations in tem- 
perature to which it was exposed. Consequently 
present-day specifications for steel boiler plate call for 
tensile strengths running from 55,000 to 66,000 lbs., 
usually 60,000 lbs. per sq. in. Dr. Thurston gives 
what he calls "good specifications" for boiler steel as 
follows: ''Sheets to be of uniform thickness, smooth 
finish, and sheared closely to size ordered. Tensile 
strength to be 60,000 lbs. per sq. in. for fire box sheets 
and 55,000 lbs. per sq. in. for shell sheets. Work- 
ing test: a piece from each sheet to be heated to a 
dark cherry red, plunged into water at 60° and bent 
double, cold, under the hammer. Such piece to show 
no flaw after bending. The U. S. Board of Supervising 
Inspectors of Steam Vessels prescribes, in Section 3 of 
General Rules and Regulations, the following method 
for ascertaining the tensile strength oi steel plate for 



THE BOILER 



297 



boilers: "There shall be taken from each sheet to be 
used in shell or other parts of boiler which are sub- 
ject to tensile strain, a test piece prepared in form 
according to the following diagram: 

•^^Sfcw/-^*. > PAraJJ_e/ Sect/on 

! ^^!U . ^ J ^ 



■■*N^ 



J^.:.f:J:^:..^^/^^j'. 



Mo///^* 



TEST PIECE. 



The straight part in center shall be 9 in. in length 
and I in. in width, marked with light prick punch 
marks at distances i in. apart, as shown, spaced so as 
to give 8 in. in length. The sample must show, when 
tested, an elongation of at least 25 per cent in a length 
of 2 in. for thickness up to }{ in. inclusive; in a length 
of 4 in., for over }( in. to yV i^- inclusive; in a length 
of 6 in., for all plates over y^- in. and under i^ in. in 
thickness. The samples shall also be capable of being 
bent to a curve of which the inner radius is not greater 
than ij^ times the thickness of the plates, after having 
been heated uniformly to a low cherry red and 
quenched in water of 82° F." 

Punched and Drilled Plates. Much has been written 
on this subject, and it is still open for discussion. If 
the material is a good, soft steel, punched sheets are 
apparently as strong and in some instances stronger 
than drilled, especially is this the case with regard to 
the shearing resistance of the rivets, which is greater 
with punched than with drilled holes. 

Concerning rivets and rivet iron and steel Dr. 



298 



ENGINEERING 



Thurston has this to say in his "Manual of Steam 
Boilers": ''Rivet iron should have a tenacity in the 
bar approaching 60,000 lbs. per sq. in., and should be 
as ductile as the very best boiler plate when cold. A 
good 5/8-in. iron rivet can be doubled up and hammered 
together cold without exhibiting a trace of fracture." 
The shearing resistance of iron rivets is about 85 per 
cent and that of steel rivets about "jj per cent of the 
tenacity of the original bar, as shown by experiments 
made by Greig and Eyth. The researches made by 
Wohler demonstrated that the shearing strength of 
iron was about four-fifths of the tensile strength. 

The tables that follow have been compiled from the 
highest authorities and show the results of a long and 
exhaustive series of tests and experiments made in 
order to ascertain the proportions of riveted joints that 
will give the highest efficiencies. 

The following Table ii gives the diameters of rivets 
for various thicknesses of plates and is calculated 
according to a rule given by Unwin. 

TABLE II 

Table of Diameters of Rivets* 



Thickness of 
Plate 


Diameter of Rivet 


Thickness of Plate 


Diameter of Rivet 


1/4 inch 

»/l6 " 
% " 

Vie " 

V2 " 


V2 inch 


9/ie inch 

% " 
•V4 " 
Vs " 
1 


Vs inch 

IV4 " 



The efficiency of the joint is the percentage of the 
strength of the solid plate that is retained in the joint, 



* Machine design— W. C. Unwin. 



THE UOILEU 



299 



and it depends upon the kind of joint and method of 
construction. 

If the thickness of the plate is more than ^ in., the 
joint should always be of the double butt type. 

The diameters of rivets, rivet holes, pitch and 
efficiency of joint, as given in the following Table 12, 
which was published in the "Locomotive" several 
years ago, were adopted at the time by some of the 
best establishments in the United States.* 

TABLE 12 

Proportions and Efficiencies of Riveted Joints 



Thickness of plate 

Diameter of rivet 

Diameter of rivet-hole 

Pitch for single riveting 

Pitch for double riveting 

Efficiency — single-riveted joint 
Efficiency — double-riveted joint 



Inch 


Inch 


Inch 


Inch 


V4 


v,« 


% 


V,n 


'Ih 


"/,« 


■'U 


''/u 


''U 


■'U 


!«/,« 


V, 


2 


2V,6 


2V« 


2«/,« 


3 


3Vs 


3V4 


33/s 


.66 


.64 


.62 


.60 


.77 


.76 


.75 


.74 



Inch 



V2 
% 

2V4 
31/2 

.58 
.73 



Concerning the proportions of double-riveted 
butt joints, Prof. Kent says: ''Practically it may 
be said that we get a double-riveted butt joint 
of maximum strength by making the diameter of 
the rivet about 1.8 times the thickness of the plate, 
and making the pitch 4.1 times the diameter of the 
hole." 

Table 13 as given below is condensed from the report 
of a test of double-riveted lap and butt joints. f In 



* Thurston's "Manual of Steam Boilers.' 
tProc. Inst. M. E., Oct., 1888. 



300 



ENGINEERING 



this test the tensile strength of the plates was 56,000 to 
58,000 lbs. per sq. in., and the shearing resistance of. 
the rivets (steel) was about 50,000 lbs. per sq. in. 



TABLE 13 

Diameter and Pitch of Rivets — Double-riveted Joint 



Kind of Joint 


Thickness of 
Plate 


Diameter of 
Rivet 


Ratio of Pitch to 
Diameter 


Lap 
Butt 
Butt 
Butt 


f inch 
1 " 
f '' 
1 " 


0.8 inches 
0.7 '' 
1.1 " 
1.3 " 


3 . 6 inches 
3.9 '' 
4.0 '' 
3.9 " 



Lloyd's rules, condensed, are as follows: 
Lloyd's Rules — Thickness of Plate and Diameter of Rivets 



Thickness of 


Diameter of 


Thickness of 


Diameter of 


Plate 


Rivets 


Plate 


Rivets 


'Vs inch 


Vs inch 


3/^ - 


Vs inch 


Vie " 


•Vs " 


^Vl6 '' 


Vs '' 


V2 " 


3/4 " 


Vs " 


1 


%6 " • 


'U " 


^Vl6 '' 


1 


Vs " 


«/4 " 


1 


1 


"/16 " 


Vs " 







The following Table 14 is condensed from one calcu- 
lated by Prof. Kent,"*" in which he assumes the shearing 
strength of the rivets to be four-fifths of the tensile 
strength of the plate per square inch, and the 
excess strength of the perforated plate to be 10 per 
cent. 



* Kent's "Mechanical Engineer's Pocki 3ook," page 362. 



THE BOILER 

TABLE 14 



301 







Pitch 


Efficiency- 


Thickness 
of Plate 


Diameter 
of Hole 








Slnt?le 


Double 


Single 


Double 






Riveting 


Riveting 


Riveting 


Riveting 


Inches 


Inches 


Inches 


Inches 


Per Cent 


Per Cent 


'/s 


Vs 


2.04 


3.20 


57 1 


72.7 


'/16 


1 


2.30 


3.61 


56.6 


72.3 


V2 


1 


2.14 


3.28 


53 3 


70.0 


V2 


IVs 


2.57 


4.01 


56.2 


72.0 


%6 


1 


2.01 


3.03 


50.4 


67.0 


»/ie 


IVs 


2.41 


3.69 


53.3 


69.5 


«/l6 


1V4 


2.83 


4.42 


55.9 


71.5 


% 


1 


1.91 


2.82 


47.7 


64 6 


% 


IVs 


2.28 


3.43 


50.7 


67.3 


Vs 


1V4 


2.67 


4.10 


53.3 


69.5 



Another table of joint efficiencies as given by Dr. 
Thurston* is as follows, slightly condensed from the 
original calculation: 



TABLE IS 

Single riveting 

Plate thickness „ Vie" %' ' Vie" V2" 



% 



^U" Vs" 1" 



Efficiency 55 .55 .53 .52 .48 .47 .45 .43 

Double riveting 

Plate thickness, ^/g" Vie" V2" V4" %" 1" 
Efficiency 73 .72 .71 .66 .64 .63 

The author has been at considerable pains to compile 
Tables 16, 17 and 18, giving proportions and efficiencies 
of single lap, double lap and butt, and triple-riveted 
butt joints. The highest authorities have been con- 
sulted in the computation of these tables and great 
care exercised in the calculations. 



♦Thurston's "Manual of Steam Boilers," page 119. 



302 ENGINEERING 

TABLE i6 

Proportions of Single-riveted Lap Joints 



Thickness of Plate 


Diameter of Rivet 


Pitch of Rivet 


Efficiency 


Indies 


Inches 


Inches 


Per Cent 


^/l6 


Vie 


1 13 


50.5 




'Vh 


1.33 


53.3 


ii 


'l'^6 


1.55 


55.7 


% 


'U 


1.60 


53.3 


a 


'U 


2.04 


57.1 


Vie 


Vs 


1.87 


53.2 




1 


2.30 


56.6 


V2 


1 


2.14 


53.3 


a 


iVs 


2.57 


56.2 


»/l6 


1 


2.01 


50.4 




iVs 


2.41 


53.3 


<> 


1V4 


2.83 


55.9 


'(? 


IVs 


2.28 


50.7 




1V4 


2.67 


53.3 



It will be noticed that in single-riveted lap joints the 
highest efficiencies are attained when the diameter of 
the rivet hole is about 2}^ times the thickness of the 
plate, and the pitch of the rivet 2?/^ times the diameter 
of the hole. 

With the double-riveted joint it appears, according 
to Table 17, that in order to obtain the highest 
efficiency the joint should be designed so that the 
diameter of the rivet hole will be from i-f to 2 times 
the thickness of plate, and the pitch should be from 
3 J^ to 3J^ times the diameter of the hole. Concerning 
the thickness of plates Dr. Thurston has this to say:* 
*'Very thin plates cannot be w^ell caulked, and thick 
plates cannot be safely riveted. The limits are about 
^ of an inch for the lower limit, and }^ of an inch for 
the higher limit.'' The riveting machine, however, 
overcomes the difficulty with very thick plates. 

* Thurston's "Manual of Steam Boilers," page 120. 



THE BOILER 



SOS 



TABLE 17 

Proportions of Double-riveted Lap and Butt Joints 



Thickness of 


Diameter of 






Plate 


Rivet 


Pitch of Rivet 


Efficiency 


5/16 inch 


»/ie inch 


1.71 inches 


67.1 per cent 


^/l6 " 


Vs " 


2.05 " 


69.5 ' 




% " 


^U " 


2.46 '' 


69.5 ' 




% " 


% '• 


3.20 " 


72.7 ' 




V16 " 


% " 


2.21 '' 


66.2 ' 




V16 " 


Vs " 


2.86 '' 


69.4 ' 




'/16 " 


1 


3.61 '' 


72.3 ' 




V2 " 


1 


3.28 '' 


70.0 ' 




V2 " 


IVs " 


4.01 ^' 


72.0 ^ 




"/le " 


1 


3.03 " 


67.0 ' 




%6 " 


IVs " 


3.69 '' 


69.5 ' 




%6 " 


1V4 " 


4.42 '' 


71.5 ' 




% " 


IVs " 


3.43 " 


67.3 ' 




% " 


1V4 " 


4.10 '' 


69.5 ' 




3/4 " 


1 


2.50 " 


72.0 ' 




% " 


IV, " 


3.94 " 


74.2 ' 




1 " 


1V4 " 


4.10 " 


76.1 ' 





The triple-riveted butt joint with two welts, one in- 
side and one outside, has two rows of rivets in double 
shear and one outer row in single shear on each side 
of the butt, the pitch of rivets in the outer rows being 
twice the pitch of the inner rows. One of the welts is 
wide enough for the three rows of rivets each side of 
the butt, while the other welt takes in only the two 
close pitch rows. 

When properly designed this form of joint has a 
high efficiency, and is to be relied upon. Table 18 
gives proportions and efficiencies, and it will be noted 
that the highest degree of efficiency is shown when the 
diameter of rivet hole is from i}( to i}4 times the 
thickness of plate, and the pitch of the rivets is from 
3^ to 4 times the diameter of the hole. This, of 



304 



ENGINEERING 



course, refers to the pitch of the close rows of rivets, 
and not the two outer rows. 



TABLE i8 

Proportions of Triple-riveted Butt Joints with Inside and 
Outside Welt 



Thickness of 


Diameter of 


Pitch of 


Pitch of 


Eflftciency 
Per Cent 


Plate 


Rivet 


Rivet 


Outer Rows 


Inches 


Inches 


Inches 


Inches 


% 


^^/l6 


3.25 


6.5 


84 


7l6 


1^16 


3.25 


6.5 


85 


V2 


'Vie 


3.25 


6.5 


83 


»/ia 


Vs 


3.50 


7.0 


84 


% 


1 


3.50 


7.0 


86 


^/4 


IV16 


3.50 


7.0 


85 


Vs 


IVs 


3.75 


7.5 


86 


1 


1V4 


3.87 


7.7 


84 



Some simple rules are given in Chapter I, Part I, for 
finding the percentage of efficiency, or in other words 
the ratio of the strength of the riveted joint to the 
strength of the solid plate. In those calculations the 
tensile strength of the rivets was assumed to be 38,000 
to 40,000 lbs. per sq. in. The highest efficiency is 
attained in a riveted joint when the tensile strength of 
the rods from which the rivets are cut approaches that 
of the plates, and when the proportions of the joint 
are such that the tensile strength of the plates, the 
shearing strength of the rivets, and the crushing 
resistance of the rivets and plate, for a given section 
or unit strip, are as nearly equal as it is possible to 
secure them. 

A few examples of calculations for efficiency will be 
given, taking the three forms of riveted joints in most 
common use. The following notation will be used 
throughout: 



THE BOILER 



305 



T.S. = Tensile strength of plate per square inch. 
T = Thickness of plate. 

C = Crushing resistance of plate and rivets. 
A = Sectional area of rivets. 
S = Shearing strength of rivets. 
D = Diameter of hole (also diameter of rivets 

when driven). 
P = Pitch of rivets. 
In the calculations that follow T.S. will be assumed 
to be 60,000 lbs., S will be taken at 45,000 lbs., and the 
value of C may be assumed to be 90,000 to 95,000. 

Fig. 97 shows a double-riveted lap joint. The style 
of riveting in this joint 
is what is known as 
chain riveting. 

In case the rivets are 
staggered, the same 
rules for calculating 
the efficiency will hold 
as with chain riveting, 
for the reason that 
with either style of 
riveting the unit strip 
of plate has a width equal to the pitch or distance p. 
Fig. 97. ^ 

The dimensions of the joint under consideration are 
as follows: P = 314^ in., T = -^^^ in., D = i in. (which is 
also diameter of driven rivet). 

The strength of the unit strip of solid plate is 
PxTxT.S. = 85,312. 

The strength of net section of plate after drilling is 
P - D X T X T.S. = 59,062. 

The shearing resistance of two rivets is 2A x S = 70, 
686. 




FIGURE 97. 



306 



ENGINEERING 



The crushing resistance of rivets and plate is 
Dx2xTxC = 78,750. 

It thus appears that the weakest part of the joint is 
the net strip or section of plate, the strength of which 
is 59,062 and the efficiency = 59,062 x 100 - 85,312 = 
69.2 per cent. 

A double-riveted butt joint is illustrated by Fig. 
98, and the dimensions are as follows: 

P, inner row 
of rivets = 2^ 
in. 

P', outer row 
of rivets = 5^^ 
in. 

Tof plate and 
butt straps = y\ 
in. 

Dof hole and 
driven rivet = i 
in. 

Failure may 

occur in this joint in five distinct ways, which will be 
taken up in their order. 

1. Tearing of the plate at the outer row of rivets. 
The net strength at this point is P — DxTxT.S., 
which, expressed in plain figures, results as follows: 
5.5 - I X .4375 X 60,000 = 118,125. 

2. Shearing two rivets in double shear and one in 
single shear. Should this occur, the two rivets in the 
inner row would be sheared on both sides of the plate, 
thus being in double shear. Opposed to this strain 
there are four sections of rivets, two for each rivet. 
Then at the outer row of rivets in the unit strip there 
is the area of one rivet in single shear to be added. 




FIGURE 



THE BOILER 



307 



The total resistance, therefore, is 5A x S as follows: 
.7854 X 5x45,000= 176,715- 

3. The plate may tear at the inner row of rivets and 
shear one rivet in the outer row. The resistance in 
this case would be P' — 2D x T x T.S. + A x S as 
follows: 5.5 - 2 X .4375 ^ 60,000 + .7854 X 45,000 = 
127,218. 

4. Failure may occur by crushing in front of three 
rivets. Opposed to this is 3D xTxC, orix3x .4375 ^ 
95,000 = 124,687. 

5. Failure may occur by crushing in front of two 
rivets and shearing one. The resistance is represented 
by 2D X T X C + lA X S; expressed in figures, i x 2 x 
•4375 >< 95,000+ .7854 X 45,000 - 118,468. 

The strength of a solid strip of plate 5J^ in. wide 
before drilling is P' x T x T.S. , or 5. 5 x .4375 ^ 60,000 = 
144,375, ^^d the efficiency of the joint is 1 18, 125 x 100 ^ 
144,375 = 81.1 per cent. 

A triple-riveted butt joint is shown in Fig. 99, the 
dimensions of 
which are as fol- 
lows: 

T = A in. 



D-=if in. 

A = .69 in. 

P =3^8 in. 

P' = 6% in. 

Failure may 
occur in this 
joint in either 
one of five 
ways. 

I. By tearing the plate at the outer row of rivets 
where the pitch is 6^ in. The net strength of the unit 




FIGURE 99. 



308 ENGINEERING 

strip at this point is P' — D x T x T.S., found as follows: 
6.7s - -9375 X -4375 x 60,000 = 152,578. 

2. By shearing four rivets in double shear and one 
in single shear. In this instance, of the four rivets in 
double shear, each one presents two sections, and 
the one in single shear presents one, thus making 
a total of nine sections of rivets to be sheared, 
and the strength is 9A x S, or .69 x 9 x 45,000 = 
279,450. 

3. Rupture of the plate at the middle row of rivets 
and shearing one rfvet. Opposed to this strain the 
strength is P' - 2D x T x T.S. -f- lA x S, equivalent to 
6.75 - (.9375 X 2) X .4375 X 60,000 + .69 X 90,000 = 
190,068. 

4. Crushing in front of four rivets and shearing one 
rivet. The resistance in this instance is 4D x T x C + 
lA x S, or .9375 X 4 X .4375 X 90,000 + .69 X 45,000 = 
178,706. 

5. Failure may be caused by crushing in front of 
five rivets, four of which pass through both the 
inside and outside butt straps, while the fifth rivet 
passes through the inside strap only, and the resist- 
ance is 5D X T X C, equivalent to .9375 x 5 x 90,000 = 

184,570. 

The strength of the unit strip of plate before drilling 
is P' x T X T.S., or 6.75 x .4375 ^ 60,000 = 177,187, and 
the efficiency is 152,578 x 100 -5- 177,187 = 86 pet 
cent. 

With the constantly increasing demand for higher 
steam pressures, the necessity for higher efficiencies in 
the riveted joints of boilers becomes more apparent, 
and of late years quadruple and even quintuple-riveted 
butt joints have in many instances come into use. The 
quadruple butt joint when properly designed show^s a 



THE BOILER 



309 



high efficiency, in some cases as high as 94.6 per cent. 
Fig. 100 illustrates a joint of this kind, and the 
dimensions are as follows: 

T=>^ in. 

D = ifin. 

A = .69 in. 

P, inner rows = 3^ in. 

P\ 1st outer row = y^ in. 

V\ 2d outer row = 15 in. 

The two inner rows of rivets extend through the 




FIGURE 100. 



main plate and both the inside and outside cover 
plates or butt straps. 

The two outer rows reach through the main plate 
and inside cover plate only, the first outer row having 
twice the pitch of the inner rows, and the second 
outer row has twice the pitch of the first. 



310 ENGINEERING 

Taking a strip or section of plate 15 in. wide (pitch 
of outer row), there are four ways in which this joint 
may fail. 

1. By tearing of the plate at the outer row of rivets. 
The resistance is P'' — D x T x T.S., or 15 — .9375 x 
,5 x 60,000 = 421,875. 

2. By shearing eight rivets in double shear and three 
in single shear. The strength in resistance is 19A x S, 
or .69 X 19 X 45,000 = 589,950. 

3. By tearing at inner rows of rivets and shearing 
three rivets. The resistance is P" — 4D x T x T.S. + 
3A X S, or 15 -(.9375 X 4) X .5 X 60,000+ .69 X 3 x45,ooo = 
430,650. 

4. By tearing at the first outer row of rivets, where 
the pitch is 7^ in., and shearing one rivet. The 
resistance is P" — 2D x T x T.S. + A x S, or 15 — (.9375 x 
2) X .5 X 60,000 -h .69 X 45,000 = 424,800. 

It appears that the weakest part of the joint is at the 
outer row of rivets, where the net strength is 421,875. 
The strength of the solid strip of plate 15 in. wide 
before drilling is P" x Tx T.S., or 15 x .5 x 60,000 = 
450,000, and the efficiency is 421,875 x 100 -^ 450,000 = 
93.7 per cent. 

Staying Flat Surfaces. The proper staying or bracing 
of all flat surfaces in steam boilers is a highly important 
problem, and while there are various methods of 
bracing resorted to, still, as Dr. Peabody says, "the 
staying of a flat surface consists essentially in holding 
it against pressure at a series of isolated points which 
are arranged in regular or symmetrical pattern." The 
cylindrical shell of a boiler does not need bracing for 
the very simple reason that the internal pressure tends 
to keep it cylindrical. On the contrary the internal 
pressure has a constant tendency to bulge out the flat 



THE BOILER 



311 




FIGURE 101. 



surface. Rule 2, Section 6, of the rules of the U. S. 
Supervising Inspectors provides as follows: ''No braces 
or stays hereafter to be employed in the construction 
of boilers shall be 
allowed a greater 
strain than 6,000 lbs. 
per sq. in. of sec- 
tion." 

The method to be 
employed in staying 
a boiler depends upon the type of boiler and the pressure 
to be carried. Formerly when comparatively low pres- 
sures were used (60 to 75 lbs. per sq. in.) the diagonal 
crow foot brace was considered amply sufficient for stay- 
ing the flat heads of boilers of the cylindrical tubular 
type, both above and below the tubes, but in the present 
age, when much higher pressures are demanded, 
through stay rods are largely employed. These are 
soft steel or iron rods ij^ to 2 in. in diameter, extend- 
ing through from head to head, with a pull at right 
angles to the plate, thus having a great advantage 
over the diagonal stay in that the pull on the diagonal 

tay per square inch of 
section is more than 5 
per cent in excess of 
what a through stay 
would have to resist 
under the same condi- 
tions of pressure, etc. 
The method of calculation for diagonal bracing is 
given in Chapter I and will not be discussed here. 

The weakest portion of the crow foot brace when in 
position is at the foot end, where it is connected to the 
head by two rivets. With a correctly designed brace 




FIGURE 102. 



812 



ENGINEERING 




■FIGURE 103. 



the pull on these rivets is direct and the tensile strength 
of the material needs to be considered only, but if the 
form of the brace is such as to bring the rivet holes 
above or below the center line of the 
brace, or if the rivets are pitched too 
far from the body of the brace, there 
will be a certain leverage exerted upon 
the rivets in addition to the direct pull. 
Fig. loi shows a brace of incorrect 
design and Figs. 102 and 103 show 
braces designed along correct lines. 

Other methods of staying, besides 
the crow foot brace and through stays, 
consist of gusset stays, and for locomo- 
tives and other fire box boilers screwed 
stay bolts are employed to tie the fire 
box to the external shell. The holes for these stay 
bolts are punched or drilled before the fire box is put 
in place. After it is in and riveted along the lower 
edge to the foundation ring, or mud ring as it is some- 
times called, a continuous thread is tapped in the 
holes in both the outside plate and the fire sheet 
y running a long tap through both plates. The 
steel stay bolt is then screwed through the plates 
and allowed to project enough at each end to permit 
of its being riveted cold. Stay bolts are liable 
to be broken by the unequal expansion of the fire 
box and outer shell, ana a small hole should be 
drilled in the center of the bolt, from the outer end 
nearly through to the inner end. Then in case a bolt 
breaks, steam or water will blow out through the small 
hole, and the break will be discovered at once. The 
problem of properly staying the flat crown sheet of a 
horizontal fire box boiler, especially a locomotive 



THE BOILER 313 

boiler, is a very difficult one and has taxed the inven- 
tive genius of some of the most eminent engineers. 

Before the invention of the Belpaire boiler, with its 
outside or shell plate flat above the fire box, the only 
method of staying the crown sheet was by the use of 
cumbersome crown bars or double girders extending 
across the top of the crown sheet and supported at the 
ends by special castings that rest on the edges of the 
side sheets and on the flange of the crown sheet. At 
intervals of 4 or 5 in. crown bolts are placed, having 
the head inside the fire box and the nut bearing on a 
plate on top of the girder. There is also a thimble for 
each bolt to pass through, between the top of the 
crown sheet and the girder. These thimbles maintain 
the proper distance between the crown sheet and 
girder and allow the water to circulate freely. 

The Belpaire fire box dispenses with girders and 
permits the use of through stays from the top of the 
flat outside plate through the crown sheet and secured 
at each end by nuts and copper washers. 

For simplicity of construction and great strength the 
cylindrical form of fire box known as the Morison 
corrugated furnace has proved to be v^y successful. 
This form of fire box was in 1899 applied to a loco- 
motive by Mr. Cornelius Vanderbilt, at the time assist- 
ant superintendent of motive power of the New York 
Central and Hudson River R. R. This furnace was 
rolled of ^-in. steel, is 59 in. internal diameter and 11 
ft. 2}{ in. in length. It was tested under an external 
pressure of 500 lbs. per sq. in. before being placed in 
the boiler. It is carried at the front end by a row of 
radial sling stays from the outside plate, and supported 
at the rear by the back head. Figs. 104 and 105 show 
respectively a sectional view and an end elevation of 



314 



ENGINEERING 




this boiler. It will 
be seen at once 
that the question 
of stays for a fire 
box of this type 
becomes very sim- 
ple. The boiler 
lias proved to be 
so satisfactory that 
the company has 
since had five more 
of the same type 
constructed. 

Gusset stays are 
used mainly in 
boilers of the Lan- 
cashire model and 
are t r i a n g ular- 
shaped plates 
sheared to the 
proper form and 
having two angle 
irons riveted to the 
edges that come 
against the shell 
and the head. The 
angle irons are 
then riveted to the 
shell and the flat 
head. This form 
of brace is simple 
and solid, but its 
chief defect is, 
that it is very rigid 



}i=^5^i 



THE BOILER 



315 



and does not allow for the unequal expansion of the in- 
ternal furnace flues and the shell. Fig. io6 illustrates a 
gusset stay and the method of applying it. 

Coming now to through stay rods, it is safe to say 
that whenever and wherever it is possible to apply 
them they should be used. In all cases they should 



^■7t^-7l 




End Elevation, 
Sftowlng Aitachmentof kong. Stays. 

FIGURE 105. 



\fr—iO^'-H Half End Elevation 
Half Section C-D. \ cf Smoke-Box, 



be placed far enough apart to allow a man to pass 
between them for the purposes of inspection and wash- 
ing out of the boiler. Through stay rods are usually 
spaced 14 in. apart horizontally and about the same 
distance vertically. The ends, as far back as the 
threads run, are swaged larger than the body, so that 
the diameter at the bottom of the thread is greater 
than the diameter of the body. There are several 



316 



ENGINEERING 



methods of applying through stays. One of the most 
common, especially for land boilers, is to allow the 
ends of the rod to project through the plates to be 
stayed, and holding them in place by a nut and copper 
washer, both inside and outside the plate. Another 
and still better plan is to riv^et 6-in. channel bars across 

the head, inside above 

the tubes, the number 

of bars depending 

upon the height of the 

segment to be stayed. 

The channel bars 

are drilled to corre- 

FiGURE 106. spond with the holes 

that are drilled in the 

plate to receive the stay rods, which latter are then 

secured by inside and outside nuts and copper washers. 





FIGURE 107. 



These channel bars act as girders and serve to greatly 
strengthen the head or flat plate. Fig. 107 will serve 
to illustrate this method. 



THE BOILER 



317 




Sometimes a combination of channel bar and 
diagonal crow foot braces is used, as shown by Fig. io8. 
A good form of diagonal crow foot stay is obtained 
by using dou- 
ble crow feet, 
made of pieces 
of boiler plate 
bent as shown 
by Fig. 109 
and riveted to 
the plate by 
four rivets. A 
hole is drilled 
through the 
body of the 
crow foot, and 
a bolt pass- 
ing through 
this secures the forked end of the stay. 

Another method of securing through stays to the 

heads is shown by Fig. no and is applied where too 

many stay rods would be required 

to connect all the points to be 

stayed. A tee iron is first riveted 

to the flat plate to be stayed, and 

two V-shaped forgings are bolted 

to it as shown. The through stay 

is then bolted to the forgings, and 

thus two points in the flat head 

are supported by one stay. It will 

readily be seen that this method will reduce the number 

of through stay rods required. 

Calculating the Strength of Stayed Surfaces. In cal- 
culations for ascertaining the strength of stayed sur- 



FIGURE 108. 




FIGURE 109. 



318 



ENGINEERING 



faces, or for finding the number of stays required for 
any given flat surface in a boiler, the working pressure 
being known, it must be remembered that each stay 
is subjected to the pressure on an area bounded by 
lines drawn midway between it and its neighbors. 
Therefore the area in square inches, of the surface to 




FIGURE 110. 



be supported by each stay, equals the square of the 
pitch or distance in inches between centers of the 
points of connection of the stays to the flat plate. 
Thus, suppose the stays in a certain boiler are spaced 
8 in. apart, the area sustained by each stay = 8x8 = 
64 sq. in., or assume the stay bolts in a locomotive fire 
box to be pitched 4^ in. each way, the area sup- 
ported by each stay bolt = 4^ x 4J^ = 20j{ sq. in. 
Again taking through stay rods, suppose, for example, 



THE BOILER SIO 

the through stays shown in Fig. 107 to be spaced 15 
in. horizontally and 14 in. vertically, the area sup- 
ported Dy each stay = 15 x 14 = 210 sq. in. 

The minimum factor of safety for stays, stay bolts 
and braces is 8, and this factor should enter into all 
computations of the strength of stayed surfaces. 

The pitch for stays depends upon the thickness of 
the plate to be supported, and the maximum pressure 
to be carried. 

In computing the total area of the stayed surface it 
is safe to assume that the flange of the plate, where it 
is riveted to the shell, sufficiently strengthens the plate 
for a distance of 2 in. from the shell, also that the 
tubes act as stays for a space of 2 in. above the top 
row. Therefore the area of that portion of the flat 
head or plate bounded by an imaginary line drawn at 
a distance of 2 in. from the shell and the same dis- 
tance from the last row of tubes is the area to be 
stayed. This surface may be in the form, of a segment 
of a circle, as with a horizontal cylindrical boiler, or 
it may be rectangular in shape, as in the case of a 
locomotive or other firebox boiler. Other forms of 
stayed surfaces are often encountered, but in general 
the rules applicable to segments or rectangular figures 
will suffice for ascertaining the areas. 

The method of finding the area of the segmental 
portion of the head above the tubes is given in Chapter 
I, pages 22 and 23, and will not be enlarged upon here, 
except to add Table 19, which covers a much greater 
number of segments than Table i, page 22, does. The 
diameter of the circle and the rise or height of the 
segment being known, the area of the segment may 
be found by the following rule: 

Rule, Divide the height of the segment by the 



320 



ENGINEERING 



TABLE 19 

Areas of Segments of a Circle 



Ratio 


Area 


Ratio 


Area 


Ratio 


Area 


Ratio 


Area 


.2 


11182 


.243 


.14751 


.286 


.18542 


.329 


. 22509 


'01 


11262 


.244 


.14837 


.287 


. 18633 


.33 


. 22603 


^02 


11343 


.245 


. 14923 


.288 


.18723 


.331 


. 22697 


.203 


11423 


.246 


. 15009 


.289 


.18814 


.332 


. 22792 


.204 


11504 


.247 


. 15095 


.29 


. 18905 


.333 


. 22886 


.205 


11584 


.248 


.15182 


.291 


. 18996 


.334 


. 22980 


,206 


11665 


.249 


. 15268 


.292 


. 19086 


.335 


. 23074 


.207 


11746 


.25 


. 15355 


.293 


.19177 


.336 


.23169 


.208 


11827 


.251 


.15441 


.294 


. 19268 


.337 


. 23263 


.209 


11908 


.252 


. 15528 


.295 


. 19360 


.338 


.23358 


.21 


11990 


.253 


.15615 


.296 


.19451 


.339 


. 23453 


.211 


12071 


.254 


.15702 


.297 


.19542 


.34 


. 23547 


.212 


12153 


.255 


. 15789 


.298 


. 19634 


.341 


. 23642 


.213 


12235 


.256 


. 15876 


.299 


.19725 


.342 


.23737 


.214 


12317 


.257 


. 15964 


.3 


.19817 


.343 


. 23832 


.215 


12399 


.258 


.16051 


.301 


. 19908 


.344 


. 23927 


.216 


12481 


.259 


.16139 


.302 


. 20000 


.345 


. 24022 


.217 


12563 


.26 


. 16226 


.303 


. 20092 


.346 


.24117 


.218 


12646 


.261 


.16314 


.304 


.20184 


.347 


.24212 


.219 


12729 


.262 


. 16402 


.305 


. 20276 


.348 


. 24307 


.22 


12811 


.263 


.16490 


.306 


.20368 


.349 


. 24403 


.221 


12894 


.264 


.16578 


.307 


. 20460 


.35 


. 24498 


.222 


12977 


.265 


.16666 


.308 


. 20553 


.351 


. 24593 


.223 


13060 


.266 


.16755 


.309 


. 20645 


.352 


. 24689 


.224 


13144 


.267 


.16843 


.31 


. 20738 


.353 


. 24784 


.225 


13227 


.268 


.16932 


.311 


. 20830 


.354 


. 24880 


.226 


13311 


.269 


.17020 


.312 


. 20923 


.355 


. 24976 


.227 


13395 


.27 


.17109 


.313 


.21015 


.356 


. 25071 


.228 


13478 


.271 


.17198 


.314 


.21108 


.357 


.25167 


.229 


13562 


.272 


.17287 


.315 


.21201 


.358 


.25263 


.23 


13646 


.273 


.17376 


.316 


.21294 


.359 


. 25359 . 


.231 


13731 


.274 


.17465 


.317 


.21387 


.36 


. 25455 


.232 


13815 


.275 


.17554 


.318 


.21480 


.361 


.25551 


.233 


13900 


.276 


.17644 


.319 


.21573 


.362 


. 25647 


.234 


13984 


.277 


.17733 


.32 


.21667 


.363 


. 25743 


.235 


14069 


.278 


.17823 


.321 


.21760 


.364 


. 25839 


.236 


14154 


.279 


.17912 


.322 


.21853 


.365 


. 25936 


.237 


14239 


.280 


. 18002 


.323 


.21947 


.366 


. 26032 


.238 


.14324 


.281 


. 18092 


.324 


. 22040 


.367 


.26128 


.239 


14409 


.282 


.18182 


.325 


.22134 


.368 


. 26225 


.24 


14494 


.283 


.18272 


.326 


. 22228 


.369 


. 26321 


.241 


14580 


.284 


. 18362 


.327 


. 22322 


.37 


.26418 


,242 


14666 


.285 


. 18452 


.328 


.22415 


.371 


.26514 



THE BOILER 

TAB LE 1 9 — Conti?iued 



321 



Ratio 


Area 


Ratio 


Area 


Ratio 


Area 


Ratio 


Area 


872 


.26611 


.405 


. 29827 


.438 


.33086 


.471 


.36373 


^73 


. 26708 


.406 


. 29926 


.439 


.33185 


.472 


.36471 


374 


.26805 


.407 


.30024 


.44 


.33284 


.473 


.36571 


.375 


.26901 


.408 


.30122 


.441 


.33384 


.474 


.36671 


.376 


. 26998 


.409 


.30220 


.442 


.33483 


.475 


.36771 


.r77 


. 27095 


.41 


.30319 


.443 


.33582 


.476 


.26871 


b78 


.27192 


.411 


.30417 


.444 


.33682 


.477 


.36971 


.379 


. 27289 


.412 


.30516 


.445 


.33781 


.478 


.37071 


.38 


. 27386 


.413 


.30614 


.446 


.33880 


.479 


.37171 


.381 


. 27483 


.414 


.30712 


.447 


.33980 


.48 


.37270 


.382 


. 27580 


.415 


.30811 


.448 


.34079 


.481 


.37370 


.383 


.27678 


.416 


.30910 


.449 


.34179 


.482 


.37470 


.384 


.27775 


.417 


.31008 


.45 


.34278 


.483 


.37570 


.385 


. 27872 


.418 


.31107 


.451 


.34378 


.484 


.37670 


.386 


.27969 


.419 


.31205 


.452 


.34477 


.485 


.37770 


.387 


. 28067 


.42 


.31304 


.453 


.34577 


.486 


.37870 


.388 


.28164 


.421 


.31403 


.454 


.34676 


.487 


.37970 


.389 


. 28262 


.422 


.31502 


.455 


.34776 


.488 


.38070 


.39 


. 28359 


.423 


.31600 


.456 


.34876 


.489 


.38170 


.391 


. 28457 


.424 


.31699 


.457 


.34975 


.49 


.38270 


.392 


. 28554 


.425 


.31798 


.458 


.35075 


.491 


.38370 


.393 


.28652 


.426 


.31897 


.459 


.35175 


.492 


.38470 


.394 


.28750 


.427 


.31996 


.46 


.35274 


.493 


.38570 


.395 


.28848 


.428 


.32095 


.461 


.35374 


.494 


.38670 


.396 


. 28945 


.429 


.32194 


.462 


.35474 


.495 


.38770 


.397 


. 29043 


.43 


.32293 


.463 


.35573 


.496 


.38870 


.398 


.29141 


.431 


.32392 


.464 


.35673 


.497 


.38970 


.399 


.29239 


.432 


.32941 


.465 


.35773 


.498 


.39070 


.4 


.29337 


.433 


.32590 


.466 


.35873 


.499 


.39170 


.401 


.29435 


.434 


.32689 


.467 


.35972 


.5 


.39270 


.402 


.29533 


.435 


.32788 


.468 


.36072 






.403 


.29631 


.436 


.32887 


.469 


.36172 






.404 


. 29729 


.437 


.32987 


.47 


.36272 







diameter of the circle. Then find the decimal opposite 
this ratio in the column headed "Area/* Multiply this 
area by the square of the diameter. The result is the 
required area. 

Example, Diameter of circle = 72 in. Height of 
segment = 25 in. 25 ^ 72 = .347, which will be found in 
the column headed *'Ratio/' and the area opposite this 



322 ENGINEERING 

is .24212. Then .24212x72x72=1,255 sq. in.,^area 
of segment. 

A boiler is 66 in. in diameter, the working pressure 
IS 100 lbs. per sq. in. The distance from the top row 
of tubes to the shell is 25 in. Required, the number 
of diagonal crow foot braces that will be needed to 
support the heads above the tubes, also the sectional 
area of each brace. The thickness of the heads is ^ 
in. and the T.S. = 55,000 lbs. per sq. in. 

Assume the head to be sufficiently strengthened by 
the flange for a distance of 2 in. from the shell, the 
diameter of the circle of which the segment above the 
tubes requires to be stayed is reduced by 2 + 2 = 4 in. 
and will therefore be 66 — 4 = 62 in. The rise or height 
of the segment above the tubes is 25 — 4 = 21 in. 
Required, the area.* 21 -62 = .338. Looking down 
the column headed ''Ratio" in Table 19, area opposite 
.338 is .23358. Area of segment = .23358 x 62 x 62 = 
897.88 sq. in. The total pressure on this area will be 
897.88 X 100 = 89,788 lbs. 

Assume the braces to be made of i^ in. round steel 
having a T.S. of 50,000 lbs. per sq. in. and to be 
designed in such a manner as to allow for loss of 
material in drilling the rivet holes in the crow feet. 
Each brace will have a sectional area of .994 sq. in., 
and using 8 as a factor of safety, the strength or safe 
holding power of each stay may be found as follows: 
.994x50,000-^8 = 6,212 lbs., and the number of stays 
required = 89,788 lbs. (total pressure) divided by 6,212 
lbs. (strength of each stay) = 14.5, or in round numbers 
15. If the stays are made of flat bars of steel the 
sectional area should equal that of the round stays, 
and the dimensions of the crow feet of allstays should 

* See rule for Table 19. 



THE BOILER 323 

be such as to retain the full sectional area of the body 
after the rivet holes are drilled. 

Each stay is connected to the plate by two ^-in. 
rivets, having a T.S. of 55,000 lbs. per sq. in. and a 
shearing strength of 45,000 lbs. per sq. in. These 
rivets are capable of resisting a direct pull of 10,818 
lbs., using 5 as a factor of safety; ascertained as fol- 
lows: 2A X 45,000 -^ 5 = 10,818 = strength of two rivets. 
They are also subjected to a crushing strain, and the 
resistance to this is D x C -^ 5, which expressed in 
figures is .875 x 90,000 -^ 5 = I5>750 lbs. 

The proper spacing comes next, and is arrived at in 
the following manner: 

Area to be stayed - 897.88 sq. in. 

Number of stays =15. 

Area supported by each stay ^ 897.88 -^ 15 = 59.8 
sq. in. 

The square root of 59.8 = 7.75 nearly, which is the 
distance in inches each way that the stays should be 
spaced, center to center. 

If through stay rods are used in place of diagonal 
braces for staying the boiler under consideration, the 
number and diameter of the rods may be ascertained 
by the following method: 

Assuming the heads to be supported by channel 
bars, as previously described, and that the stays are 
pitched 14 in. apart horizontally and 13 in. vertically, 
each stay would be required to support an area of 14 y 
13 = 182 sq. in., and the number of stays would be 
897.88 -^ 182 = 4.9, in round numbers 5. See Fig. 107. 
The pressure being 100 lbs. per sq. in., the total stress 
on each stay = 182 x 100 = 18,200 lbs. Assume the 
stay rods to be of soft steel having a T.S. of 50,000 
lbs. per sq. in., and using a factor of safety of 8, the 



3^4 ENGINEERING 

sectional area required for each stay will be found as 
follows: 18,200x8^50,000 = 2.9 sq. in., and the 
diameter will be found as follows: 2.9-^.7854 = 3.69, 
which is the square of the diameter, and the square 
root of 3.69= 1.9 in., or practically 2 in. The same 
methods of calculation are applicable to the staying of 
the heads below the tubes, also for stay bolts in fire 
box boilers. 

Strength of Unstayed Surfaces. A simple rule for 
finding the bursting pressure of unstayed flat surfaces 
is that of Mr. Nichols, published in the "Locomotive/' 
February, 1890, and quoted by Prof. Kent in his 
*Tocket-book." The rule isasfollows: ''Multiply the 
thickness of the plate in inches by ten times the tensile 
strength of the material used, and divide the product 
by the area of the head in square inches. '^ Thus, 
Diameter of head = 66 in. 
Thickness of head = s/q in. 
Tensile strength = 55,000 lbs. 
Area of head = 3,421 sq. in. 

ys X 55,000 X 10 H- 3,421 = 100, which is the number 
of pounds pressure per square inch under which the 
unstayed head would bulge. 

If we use a factor of safety of 8, the safe working 
pressure would be 100 h- 8 = 12.5 lbs. per sq. in., but as 
the strength of the unstayed head is at best an 
uncertain quantity it has not been considered in the 
foregoing calculations for bracing, except as regards 
that portion of it that is strengthened by the flange. 

In all calculations for the strength of stayed surfaces, 
and especially where diagonal crow foot stays are 
used, the strength of the rivets connecting the stay to 
the flat plate must be carefully considered. A large 
factor of safety, never less than 8, should be used, and 



THE BOILER 325 

the cross section of that portion of the foot of the stay 
through which the rivet holes are drilled should be 
large enough, after deducting the diameter of the hole, 
to equal the sectional area of the body of the stay. 

Dished Heads. In boiler work where it is possible to 
use dished, or "bumped up'' heads as they are some- 
times called, this type of head is rapidly coming into 
use. Dished heads may be used in the construction of 
steam drums, also in many cases for dome-covers, thus 
obviating the necessity of bracing. The maximum 
depth of dish, as adopted by steel plate manufacturers 
April 4, 1901, is }i of the diameter of the head when 
flanged, and if the tensile strength and quality of the 
plate from which the heads are made are the same as 
those of the shell plate, the dished head becomes as 
strong as the shell, provided the head has the same 
thickness or is slightly thicker than the shell plate. 

Welded Seams. A few boiler manufacturers have 
succeeded in making welded seams, thus dispensing 
with the time-honored custom of riveting the plates 
together. A good welded joint approaches more 
nearly to the full strength of the material than can 
possibly be attained by rivets, no matter how correctly 
designed the riveted joint may be. The weld also 
dispenses with the necessity of caulking, and a boiler 
having a perfectly smooth surface inside, such as would 
be afforded by welded seams, would certainly be much 
less liable to collect scale and sediment than would 
one with riveted joints. But in order to make a 
success of welded seams the material used must be of 
the best possible quality, and great care and skill are 
required in the work. 

The Continental Iron Works of Brooklyn, New 
York, exhibited at the St. Louis World's Fair in 1904 



326 ENGINEERING 

a welded steel plate soda pulp digester without a 
single riveted joint. The dimensions of this vessel, 
which may be likened to a cylinder boiler without flues, 
were as follows: Thickness of plate, ^ in.; diameter, 
9 ft.; length, 43 feet. The heads were dished to the 
standard depth. The safe working pressure was 125 
lbs. per sq. in. It appears not only possible, but 
probable, that the process of welding boiler joints may 
in time supplant the older custom of riveting. 



CHAPTER II 
CARE OF THE BOILER 

Washing oat the boiler — Duties of the boiler washer — How to pre« 
pare a boiler for washing — How to clean and inspect the 
inside of a boiler — Fusible plugs — Advantage of manholes, 
giving free access to top and bottom of boiler — Responsibility 
resting upon the boiler washer — Necessity of keeping water 
column clean — Scraping the flues — Fire cracks and how to 
deal with them — Firing up and how it should be done — Danger 
in too sudden heating up of a boiler — Advantages of filling a 
recently washed out boiler with warm water — Connecting 
with the main header and the safest method of procedure. 

Washing Out. In order to get the best results from 
the burning of coal or any other fuel in a boiler furnace 
it is absolutely necessary to keep the boiler as clean as 
possible, both inside and outside. In large plants the 
boiler washer and his helper are detailed to look after 
this part of the work, and while the job is by no means 
a very desirable one, it is at the same time a very 
responsible one, and much depends upon the thorough- 
ness with which the work is done. In small plants, 
consisting of one or two boilers, the engineer generally 
has to attend to the details of the work himself, and 
no matter whether the plant be large or small, the 
engineer in charge is the man above all others who 
should be most interested in seeing that thorough 
work is done, not only as a matter of safety, but for 
the sake of his reputation as an engineer. The boiler 
that is to be washed out should be allowed to gradually 
cool for ten or twelve hours. It will then be in a 
condition which will permit a man to go inside of it 

327 



328 ENGINEERING 

and do effective work, and no boiler can be thoroughly 
cleaned and inspected unless the boiler washer does 
go inside. 

These remarks apply, of course, to horizontal tubular 
or flue boilers and water tube boilers having drums 
large enough for a man to crawl into. Some types of 
internally fired boilers are provided with man-holes, 
but the majority of them have only hand-holes into 
which the hose for washing out may be inserted. 

After the water has been allowed to run out, the first 
step in washing out a boiler is to remove all the loose 
mud and scale possible by means of a steel scraper 
fitted to a long handle and introduced through the 
man-hole in the bottom part of the head. This will 
prevent the scale from getting into the blow-off pipe 
and stopping the flow of the water used for washing 
the boiler. If there is a man-hole on top, the next 
thing in order is to take the hose in through it and 
give the sides of the shell and also the tubes a good 
cleaning. 

Sometimes it happens that where an exhaust heater 
of the open type is used, oil will find its way into the 
boiler and, mixing with the mud, will form a thick 
pasty-like substance on the sides of the boiler along 
the water line. This should be carefully scraped off 
and removed, as any matter containing oil or grease is 
a very dangerous thing to have inside a boiler. 

After cleaning the upper part of the boiler, it should 
be inspected for loose braces or rivets. This can best 
be accomplished by tapping the parts with a light 
hammer. A solid rivet will give a clear metallic 
sound, and a little practice will enable one to easily 
detect the sound of a loose brace or broken rivet. 

Signs of corrosion or pitting of the shell along the 



CARE OF THE BOILER 329 

water line should also be carefully searched for. 
Fusible plugs, to be effective, must be kept clean,, and 
the only opportunity for cleaning them is at the time 
of washing out the boiler. Therefore while working on 
the upper part of the boiler, attention should be given 
to the fusible plug. If it is one of the ordinary kind, 
screwed into the back head above the tubes, it should 
be taken out and cleaned and before replacing it the 
thread should be well coated with a mixture of cylinder 
oil and plumbago, which will prevent it from sticking. 
If the fusible plug is one of the type consisting of a 
brass tube extending from the top of the shell to the 
water level, the lower end of this tube should be 
cleaned of all mud or scale. 

Having thus finished above the tubes, the mud and 
scale should again be scraped from the bottom, after 
which the hose should be inserted through the front 
man-hole that should be in every horizontal boiler. 

Some authorities argue that a man-hole should not 
be cut in the bottom part of a boiler head, giving as 
their reason that it weakens the head, but the logic is 
not sound, for the reason that the man-hole can be 
reenforced in such a manner as to make it fully as 
strong as the solid sheet, and when we consider the 
great advantage of having a man-hole in the bottom, 
both as regards washing out and also for repairs, it is 
plain that it is really a necessity. 

After washing out all the loose mud and scale that 
it is possible to get from the bottom, the boiler washer 
should next go inside and, with scrapers and tools 
made for the purpose, he should scrape and chip off 
all the scale that he can from the bottom, because 
there is where lies the greatest danger from burnt 
sheets caused by accumulations of scale preventing the 



330 ENGINEERING 

water from getting to the metal. Much good work 
may be accomplished in this way and no boiler washer 
should consider the job complete until he has gone 
through the boiler both top and bottom, and not only 
cleaned but inspected it. Any loose rivets, broken or 
loose braces, signs of corrosion or pitting should be at 
once reported to the chief engineer or superintendent. 

It will thus be seen that great responsibility rests 
with the boiler washer, for the reason that he is the 
man that is in closest touch with the inside of the 
boiler, and it is due to the manner in which he does 
his work inside the boiler whether a defect is discovered 
and repaired in time or whether it is allowed to go 
until the result is often a grave disaster. The author 
desires to enter a plea for this hard-worked and too 
often underpaid craftsman, and hereby expresses the 
wish that his services were better appreciated. 

The water column or combination should receive 
particular attention each time the boiler is washed out. 
The lower pipe leading to the boiler is liable to become 
clogged with scale, and if not cleaned regularly it is 
sure to cause trouble by preventing a free flow of the 
water from the boiler to the gauge glass. 

If the boiler is of the horizontal tubular type, the 
tubes should be scraped inside, and with water tube 
boilers use the steam jet to blow the soot and ashes 
from between the tubes. Soot, in addition to choking 
the draft, is also a non-conductor of heat. 

After the hand-hole and man-hole plates have been 
replaced the boiler may be filled with water to the 
proper level, and while this is being done it is in order 
to take a look into the furnace for any broken grates 
or accumulations of clinkers on the side walls or bridge 
wall. These clinkers should be chipped off, also the 



CARE OF THE BOILER 331 

bottom of the boiler should be swept clean of ashes and 
examined for any defects, such as fire cracks about 
the rivets most exposed to the heat. These cracks 
may often exist some time before being discovered 
unless a close inspection is made. They are small 
cracks radiating from the rivet holes outward past the 
rivet heads one-half to three-quarters of an inch, and 
are always liable to extend farther until they become a 
source of danger unless arrested in time. They may 
be closed up sometimes with the caulking tool, but if 
one should be found several inches in length, a hole 
should be drilled at the outer end of the crack and a 
rivet put in. This will generally stop it. Fire cracks 
occur in the girth seams only, and especially the seam 
nearest the fire. 

It is essential that the bridge walls of horizontal 
boilers be kept in good repair, in order that as much 
fire brick surface as possible may be exposed to the 
heat. This will greatly aid combustion and prevent 
smoke. 

Firing Tip. After the boiler washer has completed 
his task the next thing in order is firing up, and in 
doing this if care and good judgment are not exercised 
there is danger of doing much damage to the boiler, 
especially if it has been filled with cold water. A 
very light fire should be started at first and kept that 
way until the water gets to the boiling point at least, 
after which the fire may be gradually increased until 
the steam gauge shows a few pounds pressure, when it 
will be safe to urge the fire still more. The bad effects 
resulting from the unequal expansion or contraction 
of the sheets and undue stress upon the rivets, all 
caused by rapid changes of the temperature of the 
boiler from hot to cold or vice versa, cannot be 



332 ENGINEERING 

guarded against too carefully, and they are liable to be 
brought about in two ways: first, by haste in cooling 
down a hot boiler that is to be washed out, and 
secondly, by starting a heavy fire under a cold boiler. 
That part of the boiler most exposed to the heat will 
become hot while other parts farthest removed from 
the fire may still be cold. Very often there is a 
difference of 150° or 200° in the temperature of 
different parts of the boiler for a time during the firing 
up process, and the same dangerous conditions may be 
caused also by blowing all the water out of a boiler 
while under a pressure of 15 or 20 lbs., as is the custom 
of some persons when preparing a boiler for washing 
out. Either custom cannot be too strongly condemned. 

Sometimes a boiler is needed in a hurry after having 
been washed out, and in such an emergency it should 
be filled with warm water; in fact, it is better to always 
fill a boiler with warm water if it is possible to do so 
after washing out. 

Connecting with the Main Header. When the gauge 
shows a pressure that is within 10 or 15 lbs. of being 
the same as that carried on the other boilers it should 
be watched closely, and when the pressure becomes 
the same as that in the main the connecting valve 
should be opened slightly, just sufficient to allow a 
light flow of steam through it, which can be easily 
detected by placing the ear near the valve chamber. 
This steam may be passing fromi the boiler to the 
header or vice versa, but whichever way it is going the 
valve should not be opened any farther until the pres- 
sure in the main pipe and in the boiler is equalized, 
when it will be found that the valve may be opened 
easily. While connecting the boiler the dampers 
should be closed. 



CARE OF THE BOILER 333 

Care should always be exercised in connecting a 
recently fired up boiler, and the engineer should be 
certain that the steam gauge and pop valve are in 
good working order. Otherwise there is liability of a 
serious accident occurring, either in breakage of the 
steam pipe, or what is still worse, a boiler explosion 



CHAPTER III 

MECHANICAL STOKERS 

Principles involved in the action of automatic stokers— Advan- 
tages and disadvantages attending their use — Classification 
and general description of stokers — Coal-handling machinery 
— Under-feed stokers — =Mansfield chain grate stoker — Playford 
stoker — Vicars mechanical stoker — The Wilkinson stoker — 
Murphy stoker — Roney stoker — The American under-feed 
stoker — The Jones under-feed stoker — Outside furnaces— Con« 
ditions required in a boiler furnace to ensure good combus- 
tion — Hindrances to good combustion— Description of Burke 
outside furnace. 

The principles governing the operation of mechan- 
ical or automatic stokers are in the main correct, viz., 
that the suppl}^ of coal and air is continuous and that 
provision is made for the regulation of the supply of 
fuel according to the demand upon the boiler for 
steam; also that the intermittent opening and closing 
of the furnace doors, as in hand firing, thereby- 
admitting a large volume of cold air directly into the 
furnace on top of the fire, is avoided. 

Mechanical stokers have within the last twelve years 
been largely adopted in the United States, especially 
in sections where bituminous coal is the principal fuel. 
The disadvantages attending their use are: 

First, that the cost of properly installing them is so 
great that their use is practically prohibited to the 
small manufacturer. 

Second, that in case of a sudden demand upon the 
boilers for more steam the automatic stoker cannot 
respond as promptly as in hand firing, although 

334 



MECHANICAL STOKERS 335 

this objection couid no doubt be met by skillful 
handling. 

Third, the extra cost for power to operate them,- 
although this is probably offset by the diminished 
expense for labor required, as compared to hand firing. 

There are many different types of mechanical stokers 
and automatic furnaces, but they may for convenience 
be grouped into four general classes. In class one the 
grate consists of an endless chain of short bars that travel 
in a horizOi^tal J^'rection over sprocket wheels, operated 
either by a small au^^iliary engine or by power derived 
from an overhead line ol shafting in front of the boilers. 

In class two may be included stokers having grate 
bars somewhat after the ordinary type as to length and 
size, but having a continuous motion up and down or 
forward and back. This motion, though slight, serves 
to keep the fuel stirred and loosened, thus preventing 
the firing from becoming sluggish. The grate bars in 
this class of stokers are either horizontal or inclined at 
a slight angle, and their constant motion tends to 
gradually advance the coal from the front to the back 
end of the furnace. 

Class three includes stokers having the grate bars 
steeply inclined. Slow motion is imparted to the 
grates, the coal being fed onto the upper end and 
forced forward as fast as required. 

Class four includes an entirely different type of 
stoker, in that the fresh coal is supplied underneath 
the grates, and is pushed up through an opening left 
for the purpose midway of the furnace. The gases, on 
being distilled, immediately come in contact with the 
hot bed of coke on top and the result is good co*^ 
bastion. In this type of stoker steam is the active ageut 
used for forcing the coal up into the furnace, eithet 



336 



ENGINEERING 




MECHANICAL STOKERS 



337 



by means of a long, slowly-revolving screw, as in the 
American stoker, or a steam ram, as with the Jones 
under-feed stoker. A forced draft is employed, and 
the air is blown into the furnace through tuyeres 
When these stokers are intelligently handled they 
give good results, especially with cheap bituminous 
coal. The clinker formed on the grace bars or dead 
plates is easily removed. 

The coal is supplied to mechanical stokers either by 
being shoveled by hand into hoppers in front of and 
above the grates, or, as 
is the case in most of 
the large plants using 
them, it is elevated by 
machinery and depos- 
ited in chutes, through 
which it is fed to 
each boiler by gravity. 
Stokers of the chain 
grate variety are usu- 
ally constructed so that 
they may be withdrawn 
from underneath the 
boiler in case repairs are 
necessary. The coal, 
either nut or screen- 
ings, is fed into a hop- 
per in front of and 
above the level of the grate, and is slowly carried 
along towards the rear end. The ash drops from 
the grate as it passes over the sprocket wheel at 
the rear. 

Fig. Ill shows a battery of Babcock and Wilcox 
water tube boilers fitted with chain grate stokers. The 




FIGURE 112. 

CAHALL VERTICAL BOILER WITH 

CHAIN GRATE STOKER ATTACHED 



338 



ENGINEERING 



buckets for elevating the coal to bins overhead, from 
whence it is fed by gravity to the stokers, are not 
shown. These buckets or carriers may also be utilized 
for conveying the ashes from the boiler-room. 




o 
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Q 

W 



o c 

W 
M 

C 



Fig. 112 is a sectional view of a vertical Cahall 
boiler with a Mansfield chain grate stoker, and Fig. 113 
sfiows the same stoker withdrawn from the boiler. 

The Coxe mechanical stoker operates upon the same 



MECHANICAL STOKERS 



339 



general principles as do those previously described, 
being of the chain grate type, but it has in addition a 
series of air chambers just underneath the upper 
traveling grate. These air chambers are made of sheet 
iron and are open at the top and provided with dampers 
for regulating the air pressure for different sections of 
the grate. The air blast is supplied by a fan. Another 
feature of this stoker is a water chamber for the bottom 
section of the grate to travel through on its return. 




FIGURE 114. 

The Playford stoker has wrought iron T bars extend- 
ing across the furnace and attached to the traveling 
chains. These T bars carry the small cast iron sections 
composing the grate. A screw conveyor is also 
placed in the ash pit for the purpose of carrying the 
ashes from the rear to the front of the pit. Fig. 114 is 
a sectional view of the Playford stoker attached to a 
water tube boiler. 

In class two may be included stokers halving the 
grates inclined more or less. In some varieties the 
grates incline from front to rear, while in others they 



340 ENGINEERING 

are made to incline from the side walls towards the 
center line of the furnace. 

In the Vicars mechanical stoker the grate bars are 
somewhat of the shape of the ordinary grate and lie in 
two tiers in a horizontal position. The lower or back 
tier next the bridge wall is stationary and is placed 
there for the purpose of catching what coal is carried 
over the ends of the upper or moving grate bars. 
These have a slow reciprocating motion which 
gradually moves the hot coke back towards the bridge 
wall The coal is fed from a hopper into two com- 
partments, from which it is pushed by reciprocating 
plungers onto a coking plate and from thence it 
passes to the grate bars. The motion of these bars 
has several intermediate variations, from a state of 
rest to a movement of 3>^ in. They have a simul- 
taneous movement forward by which the fuel is 
advanced, but on the return movement the bars act at 
separate intervals. In this manner the fuel remains 
undisturbed b}^ the return motion of the grates. Fig. 
115 illustrates this stoker. 

In the Wilkinson stoker. Fig. 116, the grate bars 
are hollow and are set at an angle of 20°, the inclina- 
tion being from front to back. Each bar is stepped 
along its fire surface and on the rise is perforated with 
a long, narrow slot. A steam pipe extends along the 
front of the furnace and from this pipe small branch 
pipes lead into the ends of the grate bars, which latter 
are in fact a series of hollow trunks with their front 
ends open. When in operation a steam blast is 
admitted to each of the several trunk grate bars 
through the small branch pipes, and this blast induces 
an air current of more or less pressure, which finds an 
outlet through the narrow slots in the stepped fire 



MECHANICAL STOKERS 



341 



surface of the grates and directly into and through the 
burning mass of fuel. A slow reciprocating motion is 
imparted to the grates by means of cranks and links 
operated from an overhead shaft; see Fig. 117. These 
cranks are set alternately at go° with each other, thus 
giving a forward movement to one-half of the grate 
bars while at the 
same time the 
other half is 
moving back- 
ward. In this 
manner the fuel 
is kept slowly 
moving down 
the inclined 
grates. 

The Murphy 
Automatic Fur- 
nace, a sectional 
view of which is 
shown in Fig. 
118, has the 
grates inclined 
inwards from 
the side walls, 
while a fire 
brick arch is 
sprung from 
side to side to cover the entire length of the grate. 
The coal is shoveled or fed by carrier into the 
coal magazines, one on each side, as shown in the 
cut. If the furnace is placed directly under the boiler 
it necessitates putting these coal magazines within the 
side walls, but as the Murphy furnace is usually con- 




FIGURE 115. 



342 



ENGINEERING 



structed at the present day as an outside furnace, the 
coal magazines are independent of the boiler walls. 
The bottom of each magazine is used as a coking 




plate, against which the upper ends of the inclined 
grates rest. On the central part of this plate is an 
inverted open box. This is termed the "stoker box/' 



MECHANICAL STOKERS 



343 



and it is moved back and forth across the face of the 
coking plate by means of a shaft with pinions that 
mesh into racks under each end of the box. By means 




FIGURE 117. WILKINSON STOKER. 



of this motion of the stoker boxes the coal is pushed 
forward to the edge of the coking plate and from 
thence it slowly passes down over the inclined grates 



344 



ENGINEERING 



toward the center of the furnace. At this point the 
slowly rotating clinker breaker grinds the clinker and 
other refuse and deposits them in the ash pit. 




FIGURE 118. THE MURPHY AUTOMATIC FURNACE. 

Above the coking plates are the "arch plates/* upon 
which the bases of the fire brick arch rest. These 
plates are ribbed, the ribs being an inch apart, and, the 
arch resting upon these ribs, there is thus provided a 
series of air ducts by means of which the air, already 
heated by having been admitted in front and passed 
through the flues over the arch, is conducted into the 
furnace above the grates and comes directly in contact 
with the gases rising from the coking fuel. Air is also 
admitted under the coking plate and, passing up 
through the grates, serves to keep them cool and also 
furnishes the needed supply to the burning coke as it 
slowly moves down toward the center. 



MECHANICAL STOKERS 345 

The fuel is aided in its downward movement'by the 
constant motion of the grates, one grate of each pair 
being moved up and down by a rocker at the lower 
end. 

Motion is imparted to the various moving parts of 
this furnace by means of a reciprocating bar extending 
across the outside of the entire front, and to which all 
the working parts are attached by links and levers. 
This bar is operated by a small engine at one side of 
the setting, the power required being about one horse- 
power per furnace. 

The Roney stoker consists of a set of rocking stepped 
grate bars, inclined from the front towards the bridge 
wall. The angle of inclination is 37°. A dumping 
grate operated by hand is at the bottom of the incline 
for the purpose of receiving and discharging the clinker 
and ash. This dumping grate is divided into sections 
for convenience in handling. 

The coal is fed onto the inclined grates from a 
hopper in front. The grate bars rock through an arc 
of 30°, assuming alternately the stepped and the 
inclined position. Fig. 119 is a sectional perspec- 
tive view of this stoker and illustrates the working 
parts. 

The grate bars receive their motion through the 
medium of a rocker bar and connecting rod. A shaft 
extending across the front of the stoker under the 
coal hopper carries an eccentric that gives motion to 
the connecting rod and also to the pusher in the coal 
hopper. This pusher, working back and forth, feeds 
the coal over the dead plate onto the grates, and its 
range of motion is regulated by a feed wheel from no 
stroke to full stroke, according to the demand for coal. 
The motion of the grate bars may also be regulated by 



346 



ENGINEERING 



a sheath nut working on a long thread on the connect- 
ing rod. Each grate bar consists of two parts, viz., a 
cast iron web fitted with trunnions on each end that 
rest in seats in the side bearer and a fuel plate having 
the under side ribbed to allow a free circulation of 
air. 

The fuel plate is bolted to the weD and carries the 




FIGURE 119. 
SECTIONAL PERSPECTIVE OF THE RONEY MECHANICAL STOKER. 



fuel. The grates lie in a horizontal position across 
the furnace in the form of steps, and ample provi- 
sion is made for the admission of air through the 
slotted webs. A fire brick arch is also sprung 
across the furnace, covering the upper portion of the 
grate. 

This arch, being heated to a high temperature, serves 
in a measure to partly coke the coal as it passes under 
it. Air is also admitted on top of the coal at the 
front. This air is heated by its passage through a 
perforated tile over the dead plate and adjoining the 



MECHANICAL STOKERS 347 

fire brick arch. Fig. 120 shows the location of the 
arch and tile. 

In mechanical stokers of the under-feed type the air 
is supplied by forced draft. 

The American stoker consists of a horizontal con- 
veyor pipe into which the coal is fed from a hopper. 
The diameter of this pipe depends upon the quantity 
of coal to be burned, and varies from 4}^ in. for the 
smaller sizes up to 9 and 10 in. for the larger sized 
stokers. The length of the conveyor pipe for the 




I 



M^' 



FIGURE 120. 

standard lo-in. stoker is 72 in. Attached to the outer 
end of this conveyor pipe, and forming a part of it, is 
an iron box containing a reciprocating steam motor 
which, through the medium of a rocker arm and pawl 
and ratchet wheel, drives a screw conveyor shaft that 
slowly revolves within the pipe, thus forcing the coal 
forward and up through another box or trough, which 
latter is wholly within the furnace. Extending around 
the top edges of this box, and on a level with the grate 
bars, there is a series of tuyeres through which the air 
is forced 



348 



ENGINEERING 



These tuyeres, being at a high temperature, serve to 
heat the air in its passage through them, thus greatly 




aiding combustion. Fig. 121 is a longitudinal sectional 
view of this stoker. 

The speed of the screw conveyor is regulated by the 
hand throttle of the motor, according to the demand 



MECHANICAL STOKERS 



349 



for coal. With the 9-in. standard stoker from 350 to 
1,200 lbs. of coal per hour may be burned. Fig. 122 
is a view of the American stoker before being placed 
in position in the furnace. 



I 




P4 
o 

H 

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W 
o 

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o 'cO 



^"2 .^ ^ 

CO rj »-i (-> 

o a p 



1! O Q^ 

08B 



•J5 cd ce 
tUDO 



ttf 






The air jets, passing out from the tuyeres in a 
horizontal direction, and from opposite sides, cut 
through the rounded bed of coal and the gases are thus 
ignited and consumed immediately after being distilled 



350 ENGINEERING 

from the coal, while the pressure of the coal rising 
from underneath forces the already coked fuel over the 
edges of the trough or box onto the grates which 
occupy the space between the side walls and the coal 
trough. The air is first delivered from the fan into 
the air box that surrounds the coal trough on three 
sides and from thence it passes to the tuyeres. If this 
stoker is properly handled very good results may be 
obtained by its use, but, like all other devices for burn- 
ing coal under boilers, it is bad policy to endeavor to 
force it beyond its capacity. 

In the Jones under-feed stoker the coal is pushed for- 
ward and up into the furnace through a cast iron retort or 
trough. The impelling force is a steam ram connected 
to the outer end of the retort, and the speed of the ram is 
regulated automatically by the steam pressure, or by 
hand as desired. The coal is supplied to the ram through 
a cast iron hopper having a capacity of 125 to 140 lbs. 

Forced draft is also employed in this stoker, the air 
being conducted from the fan or blower through 
galvanized iron pipes into the closed ash pit, which 
really forms an air box, as the space on either side of 
the retort that is usually occupied by grate bars is in 
this case covered by solid cast iron dead plates upon 
which the coked fuel lies until it is consumed. These 
plates, being hot, serve to heat the air coming in con- 
tact with them in its passage to the cast iron tuyeres 
through which it passes to the bed of burning fuel in 
the retort. Air entirely surrounds the retort on the 
sides and back end, and is at a constant pressure in 
the ash pit, but can only pass into the furnace through 
the tuyeres, the jets of air cutting through the rounded 
heap of incandescent fuel from opposite sides and in 
a direction inclined upwards. 



MECHANICAL STOKERS 



351 



Coal is supplied to the hopper either by hand, or by 
mechanical means where the plant is fitted with coal- 
handling machinery. The opening through which it 
passes from the hopper to a position in front of the 
ram is 8 x lo in. in size. Each charge of the steam 




FIGURE 123. 

ram carries forward 15 to 20 lbs. of coal. Connected 
to the ram and moving in conjunction with it is a long 
rod extending through the retort near the bottom. 
Upon this rod are carried shoes that act as auxiliary 
plungers and facilitate the movement of the coal. 




FIGURE 124. 



Fig. 123 is a sectional view of the Jones stoker, 
showing the machine full of coal, with the ram ready 
to make a charge. Fig. 124 shows the stoker complete 
before being placed in the furnace. 



352 ENGINEERING 

It is claimed by the builders of under-feed stokers, 
and the claim appears to have good foundation, that 
by pushing the green coal up so as to meet the upper 
crust of glowing fuel the gases on being distilled 
immediately come in contact with and are consumed 
by the burning mass, and the formation of smoke is 
thus prevented. Both the Jones under-feed and the 
American stokers have proved to be very successful in 
the burning of the cheaper bituminous coals of the 
West. One feature tending to commend them is the 
fact that practically all of the coal is utilized, there 
being no waste caused by the slack coal or fine screen- 
ings dropping through the grate bars into the ash pit 
unconsumed. 

A good substitute for the mechanical stoker is an 
outside furnace, by which is meant a boiler installation 
having the furnace in front of instead of underneath 
the boiler. One of the principal hindrances to good 
combustion in the ordinary type of boiler furnace is 
the fact that the temperature of the boiler shell or 
water tubes with which the gaseous products of com- 
bustion come in contact can never be higher than the 
temperature of the water contained within the boiler. 
This temperature ranges from 297° for steam at 50 lbs. 
gauge pressure, up to 407° for 255 lbs. pressure, while 
the temperature of the furnace, according to Dr. 
Thurston and other high authorities, ranges from 2,010° 
to 2,550°. 

It is evident that perfect combustion does not take 
place until these high temperatures are reached. Each 
time the furnace is charged with fresh coal, especially 
if the boiler be hand-fired, a large volume of volatile 
gases is liberated but not consumed. If these gases 
are allowed to immediately come in contact with a 



MECHANICAL STOKERS 



353 



comparatively cool surface, as for instance the heating 

surface of the boiler, the result is a cooling of the 

gases, incomplete combustion and the formation of 

smoke and soot. If on the other hand the furnace is 

so constructed that these gaseous products first impinge 

against hot surfaces, such as fire brick arches or bafflers 

that have a temperature 

corresponding to that 

of the furnace, good 

combustion is assured. 

This condition is in a 

large degree attained 

by the use of outside 

furnaces that permit the 

construction of a fire 

brick arch to cover the 

entire grate surface. 

The Burke furnace, 
patented by James V. 
Burke of Chicago, is a 
notable example of this 
type of furnace. It is 
applicable to any type 
of stationary boiler. 
Fig. 125 shows this fur- 
nace as applied to 
tubular boilers. It con- 
sists of a fire brick arch 
extending from 6 to 8 
ft. outwards from the boiler front and of a width to 
correspond to the diameter of the boiler. The arch 
rests securely upon brick work inclosed in a well 
ventilated iron casing. There is practically no heat 
radiated from this furnace, all the heat generated 




FIGURE 125. 



354 



ENGINEERING 



by it passing to the boiler. The central portion of the 
grate bars consists of shaking grates, while the side 
bars are stationary and inclined. 

Fig. 126 is a sectional view and will serve to illustrate 
the construction of this furnace. The coal is fed 
through pockets on top on each side of the arch, the 
larger furnaces having two pockets on each side and 
the smaller sizes one. The doors in front are only 




FIGURE 126. 

opened for the purpose of cleaning fires or when first 
starting fires. The air is supplied by way of the ash 
pit, passing up through the grate bars. A portion of 
the air supply is also drawn through the ventilators and 
passes to the upper part of the furnace. The arch 
extends under the front end of the boiler 6 or 8 in. , and 
there is a bridge wall about 4 ft. back from the front 
against which the gases from the furnace impinge. 
There are 42 sq. ft. of grate surface in the larger 



MECHANICAL STOKP.RS 355 

sizes, and 22 sq. ft. in the smaller size. Good com- 
bustion is attained in this furnace, owing to the fact 
that the gases as they are distilled from the coal come 
immediately in contact with the highly heated surface 
of the arch directly over the fire. 



CHAPTER IV 

THE STEAM TURBINE 

The steam turbine — Lack of information concerning steam tur- 
bines — Points of difference between the turbine and the 
reciprocating engine — Kinetic energy in steam — Hero's steam 
turbine — Branca's steam turbine — Fundamental principles of 
■^he steam turbine — Types of steam turbines built in the 
United States — The Westinghouse- Parsons turbine — Theo- 
retical velocity of steam exhausting into a vacuum — Relation 
of bucket speed to steam speed — Speed of the Westinghouse- 
Parsons turbine — Description of cylinder and blades — Rela- 
tion of stationary to moving blades — Curvature of blades — 
Action of the steam within the turbine explained — Balancing 
pistons — Construction of bearings — A floating journal — Lubri- 
cation of bearings — Water seal packing — Speed regulation — 
Description and diagram of governor — Efficiency of steam 
turbines — Tests of Westinghouse-Parsons turbines. 

Although the turbine principle of utilizing the energy 
in steam and converting it into useful work has been 
experimented upon for many years, it is only since the 
inauguration of the twentieth century that steam 
turbines have been brought to the front as efificient 
power producers. 

There are to-day in this country four distinct types 
of steam turbines, each one of which has its own 
characteristic features distinguishing it from *:he 
others, but in each the kinetic energy and velocity of 
the expanding steam constitute the source of power. 

No<twithstanding the fact that much has been said 
and written during the past four years regarding the 
steam turbine, the machine is to-day a mystery to 
thousands of engineers, not because they do not desire 

356 



THE STEAM TURBINE 



357 



information upon the subject, but because of a lack of 
opportunities for obtaining that information. The 
author therefore considers that a space devoted to 
this subject would no doubt be of benefit to his 
readers. 

The piston of the reciprocating engine is driven back 




FIGURE 127. 

and forth by the static expansive force of the steam, 
while in the steam turbine not only the expansive force 
is made to do work, but a still more important element 
is utilized, viz., the kinetic energy or heat energy 
latent in the steam and which manifests itself in the 
rapid vibratory motion of the particles of steam 



358 



ENGINEERING 



expanding from a high to a lower pressure, and this 
motion the steam turbine transforms into work. 

One of the earliest descriptions of a device for con- 
verting the power of steam into work was recorded by 
Hero, a learned writer who flourished in the city of 
Alexandria in Egypt, in the second century before 
Christ. Hero describes a machine called an ^olipile 
or "Ball of ^olus," illustrated in Fig. 127. B is the 
boiler under which a fire was made. G is a hollow 




FIGURE 128. 

metallic globe that revolved on trunnions C and D, 
one of which terminated in a pivot at E, while the 
other was hollow and conveyed the steam generated in 
the boiler B to the interior of the globe or ball, from 
which it escaped through the hollow bent tubes H and 
I, and the reaction of the escaping steam caused the 
globe to revolve. This was the first steam turbine, and 
it worked on the reaction principle. 

Many centuries later, in the year A.D. 1629, Branca, 
an Italian, described an engine which marks a change 



THE WESTINGHOUSE PARSONS STEAM TURBINE 359 

in the method of using the steam. Branca's engine 
consisted of a boiler A» Fig. 128, from which the steam 
issued through a straight pipe and impinged upon the 
vanes of a horizontal wheel carried upon a vertical 
shaft, causing it to revolve. This device was the germ 
of the impulse turbine, and these two principles, viz., 
reaction and impulse, either one or the other and 
sometimes a combination of both, are the fundamental 
principles upon which the successful steam turbines of 
the present age operate. 

As previously stated, there are four types of steam 
turbines being manufactured in this country at present, 
viz.. 

The Westinghouse-Parsons Turbine, 

The General Electric Curtis Turbine, 

The Hamilton-Holzwarth-Rateau Turbine, and 

The De Laval Turbine. 
Each will be taken up in its regular order and its 
distinctive theoretical features studied. 

The Westinghouse-Parsons Steam Turbine is funda- 
mentally based upon the invention of Mr. Charles A. 
Parsons, who, while experimenting with a reaction 
turbine constructed along the lines of Hero's engine, 
conceived the idea of combining the two principles, 
reaction and impulse, and also of causing the steam to 
flow in a general direction parallel with the shaft of 
the turbine. This principle of parallel flow is common 
to all four types of turbines, but is perhaps more 
prominent in the Westinghouse-Parsons and less so in 
the De Laval. 

A cubic foot of steam under 100 lbs. pressure, if 
allowed to discharge into a vacuum of 28 in., would 
attain a theoretical velocity of 3,860 ft. per second and 
would exert 59,900 ft. -lbs. of energy. A law of turbo 



360 ENGINEERING 

mechanics specifies that in order to obtain the highest 
efficiency in the operation of turbines (whether water 
or steam) the relation between bucket speed and fluid 
speed (steam in this case) should be as follows: 

For purely impulse wheels, bucket speed equals 
one-half of jet speed. 

For reaction wheels, bucket speed equals jet speed. 

Assuming the velocity of the jet of steam issuing 
from the nozzle to be 4,000 ft. per second, this would 
mean a peripheral speed of 2,000 ft. per second for an 
impulse wheel, and for a wheel i ft. in diameter the 




FIGURE 129. 

speed would be 38,100 R. P. M. But such a speed is 
beyond the limits of strength of material. 

As before stated, the Westinghouse-Parsons turbine 
operates on both impulse and reaction principles, and 
by a system of compounding, which will be explained 
later on, the peripheral velocity of the machine has 
been so reduced as to bring it within practical limits 
while at the same time the power value of the steam is 
utilized to a high degree of efficiency. 

The speed of the Westinghouse-Parsons turbine 



THE WESTINGMOUSE PARSONS STEAM TURBINE 361 

varies from about 750 R. P. M. for a 5,000 K. W, 
machine to 3,600 R. P. M. for a 400 K. W. turbine. 

Fig. 129 is a general view of a 400 K. W. turbine 
generator unit. Fig. 130 shows a 600 H. P. machine 
with the upper half of the cylinder, or stator as it is 
termed, throv/n back for inspection. Fig. 131 is a 
sectional view of a Westinghouse-Parsons turbine, and 
it will be noticed that there are three sections or drums, 
graduall}' increasing in diameter from the inlet A to 




FIGURE 130. 



the third and last group of blades. This arrange- 
ment may be likened in some measure to the triple 
compound reciprocating engine. 

By reference to Fig. 130 it will be seen that the 
inside of the cylinder is studded with rows of small 
stationary blades and that the rotor or revolving part 
of the machine is also fitted with rows of small blades, 
similar in shape and dimensions to the stationary 



362 



ENGINEERING 



blades. When the upper half of the cylinder is in 
position, each row of stationary blades fits in between 
two corresponding rows of moving blades. This 
arrangement may perhaps be better understood by 
reference to Fig. 132, which illustrates the relation of 
the stationary blades to the moving blades when in 
position, and also shows by the arrows the course of 
the steam and its change of direction caused by the 
stationary blades. 

For the purpose of explanation the moving blades or 




FIGURE 131. 

vanes may be considered as small curved paddles pro- 
jecting from the surface of the rotor, and there is a 
large number of them, as, for instance, taking a 400 
K. W. machine, there are 16,095 moving blades and 
14,978 stationary blades, a total of 31,073. 

The stationary vanes, as previously explained, project 
from the inside surface of the cylinder. Both station- 
ary and moving vanes are similar in shape, and are 
made of hard drawn material, and they are set into 



THE WESTINGHOUSE-PARSONS STEAM TURBINE 363 

their places and secured by a caulking process. The 
blades vary in size from ^ to 7 in. in length, accord- 
ing to where they are used. Referring to Fig. 130, it 
will be observed that the shortest blades are placed at 
what might be termed the steam end of each section or 
drum of the rotor and cylinder, and that their length 
gradually increases, corresponding with the increased 
volume of steam, until a mechanical limit is reached, 
when a new group of blades begins on a succeeding 
drum of larger diameter. Referring to Fig. 132, 
which is a sectional view of four rows of blades, it will 

^ ^ ^ ^ ^ C^C C C ^'''^''■'oW BLADES 



i) i) )) )) i) :J) )) )) )) 






MOVING BLADES 
STATIONARY BLADES 

MOVING BLADES 



^ 



I 



FIGURE 132. 



be noticed that all the blades, whether stationary or 
moving, have the same curvature. Also that the curves 
are set opposite each other. The reason for this will 
be apparent as the diagram is studied. The steam at 
pressure P first comes in contact with row i of station- 
ary blades. It expands through this row, and in 
expanding the pressure falls to P'. 

The energy in the steam is converted into velocity, 
and it impinges upon row 2 of moving blades, driving 
them around in their course by impulse. A second 
expansion now occurs in row 2 and again the energy is 
converted into velocity, but this time the reaction of 



364 ENGINEERING 

the steam as it leaves the blades of row 2 also tends to 
impel them around in their course. The moving 
blades thus receive motion from two causes — the one 
due to the impulse of the steam striking them, and the 
other due to the reaction of the steam leaving them. 

This cycle is repeated in rows 3 and 4, and so on 
throughout the length of the rotor until the exhaust 
end is reached. 

It should be noted that the general direction taken 
by the steam in its passage through the turbine is in 
the form of a spiral or screw line about the rotor. The 
clearance between the blades as they stand in the rows 
is }i in. for the smallest size blades and J^ in. for the 
larger ones, gradually increasing from the inlet to the 
exhaust. In the 5,000 K. W. machine the clearance at 
the exhaust end between the rows of blades is i in. It 
will thus be seen that there is ample mechanical 
clearance, also allowance for lateral motion for adjust- 
ment of the rotor, although this is very slight, as the 
rotor is balanced at all loads and pressures by the 
balancing pistons PPP, Fig. 131, to which reference 
is now made. These pistons revolve within -the 
cylinder, but do not come in mechanical contact with 
it; consequently there is no friction. The diameter of 
each piston corresponds to the diameter of one of the 
three drums. 

The steam entering the chamber A through valve V 
presses against the turbine blades and goes through 
doing work by reason of its velocity. It also presses 
equally in the opposite direction against the first piston 
P, and so the shaft or rotor has no end thrust. On leav- 
ing the first group of blades and striking the second 
group the pressure in either direction is again equalized 
by the balance port E allowing the steam to press against 



THE WESTINGHOUSE-PARSONS STEAM TURBINE '365 

the second balance piston P. The same event occurs at 
group three, the steam acting upon the third piston P. 

The areas of the balancing pistons are such that, no 
matter what the load may be or what the steam pres- 
sure or exhaust pressure may be, the correct balance 
is maintained and there is practically no end thrust. 
Below is shown a pipe E connecting the back of the 
balancing pistons with the exhaust chamber. This 
arrangement is for the purpose of equalizing the 
pressure at this point with the pressure in the exhaust 
chamber B. 

It might be thought that the blades, on account of 
their being so light and thin, would wear out very fast, 
but experience so far shows that they do not. This 
may be accounted for in two ways. First, the reduc- 
tion of the velocity of the steam, the highest velocity 
in the Parsons turbine not exceeding 600 ft. a second; 
secondly, the light steam thrust on each blade, said to 
bje equal to about I oz. avoirdupois. This is far within 
the bending strength of the material. A steam strainer 
is also placed in the admission port, to prevent all 
foreign substances from entering the turbine. 

A rigid shaft and thrust or adjustment bearing 
accurately preserves the clearances, which are larger in 
this turbine than in other types, owing to the fact that 
the entire circumference of the turbine is constantly 
filled with working steam when in operation. 

The bearings shown in Fig. 131 are constructed 
along lines differing from those of the ordinary 
reciprocating engine. The bearing proper is a gun 
metal sleeve that is prevented from turning by a loose- 
fitting dowel. Outside of this sleeve are three con- 
centric tubes having a small clearance between them. 
This clearance is kept constantly filled with oil sup- 



366 ENGINEERING 

plied under light pressure, which permits a vibration 
of the inner shell or sleeve and at the same time tends 
to restrain or cushion it. This arrangement allows the 
shaft to revolve about its axis of gravity, instead of 
the geometrical axis, as would be the case if the bear- 
' ing were of the ordinary construction. The journal is 
thus to a certain degree a floating journal, free to run 
slightly eccentric according as the shaft may happen 
to be out of balance. 

A flexible coupling is provided, by means of which 
the power of the turbine is transmitted to the dynamo 
or other machine it is intended to run. The oil from 
all the bearings drains back into a reservoir, ar :■ from 
there it is forced up into a chamber, where it forms a 
static head, which gives a constant pressure of oil on 
all the bearings. A secondary valve is located at Vs, 
by means of which high pressure steam may be admitted 
to the steam space E on the same principle that 
high pressure steam is admitted to the low pressure 
cylinder of a compound engine. This valve opens 
automatically in cases of emergency, such as overload, 
failure of the condenser to work, etc. 

The shaft, where it passes through either cylinder 
head, is packed wHh a water seal packing, consisting 
of a small paddle wneel attached to the shaft, which, 
through centrifugal action, maintains a static pressure 
of about 5 lbs. per sq. in. in the water seal, thus pre- 
venting all leakage while at the same time it is 
frictionless. 

The speed of the Westinghouse-Parsons turbine is 
regulated by a fly ball governor constructed in such 
manner that a very slight' movement of the balls 
serves to produce the required change in the supply of 
steam. Fig. 133 is a diagram of the governor 



THE WESTINGHOUSE-PARSONS STEAM TURBINE 367 

mechanism. The ball levers swing on knife edges 
instead of pins. The governor works both ways, that 
is to say, when the levers are oscillating about their 
mid position a head of steam corresponding to full 
load is being admitted to the turbine, and a move- 
ment from this point, either up or down, tends to 
increase or to decrease the supply of steam. 

Referring to Fig. 133, B is a piston directly con- 




FIGURE 133. 



nected to the admission valve. Steam is admitted to 
this piston under control of the pilot valve A, which 
has a slight but continuous reciprocating motion 
derived from the eccentric rod C, and the function of 
the governor is to vary the plane of oscillation of this 
valve, thus causing it to admit more or less steam to 
piston B. The admission valve, being actuated 
exclusively by piston B, is thus caused to remain open 
for a longer or shorter period of time, according to the 
load upon the turbine. 



368 ENGINEERING 

The vibrations of the admission valve, although very 
slight, are continuous and regular, about 165 per 
minute, and are transmitted primarily by means of an 
eccentric, the rod of which is shown at C, Fig. 133. 

The governor sleeve is used as a floating fulcrum, and 
the points D and E are fixed. By means of this very 
ingenious device the steam is admitted to the turbine in 
puffs, either long or short, according to the demand for 
steam. At full load the puffs merge into an almost con- 
tinuous blast. When the load has increased to the point 
where the valve is wide open continuously, a full head of 
steam is being admitted. Beyond this the secondary 
valve comes into action, thus keeping the speed up to 
normal. 

The rotor requires perfect balancing to insure quiet 
running, but this is easily accomplished in the shop by 
means of a balancing machine used by the builders. 

Steam turbines generally show higher efficienc}^ in 
the use of steam than reciprocating engines do, and 
this fact is due to three leading causes. First, it is 
possible with the turbine to use highly superheated 
steam which, owing to the difficulties attending 
lubrication, could not be used in the reciprocating 
engine. Second, a larger proportion of the heat con- 
tained in the steam is converted into work, for the 
reason that the steam is allowed to expand to a much 
lower pressure and into a higher vacuum. In addition 
to this, the velocity of the expanding steam is utilized 
in a much higher degree in the turbine as compared 
with the reciprocating engine. Third, mechanical fric- 
tion or lost work is reduced to the minimum. Unde 
test a 400 K. W. Westinghouse-Parsons steam turbine, 
using steam at 150 lbs. initial pressure and superheated 
about 180°, consumed 11. 17 lbs. of steam per Brake 



THE WESTINGHOUSE-PARSONS STEAM TURBINE 369 

horse power hour at full load. The speed was 
3,550 R. P. M. and the vacuum was 28 in. With 
dry saturated steam the consumption was 13.5 lbs. 
per B. H. P. hour at full load, and 15.5 lbs. at one-half 
load. 

A 1,000 K. W. machine, using steam of 150 lbs. 
pressure and superheated 140°, exhausting in^o a 
vacuum of 28 in., showed the very remarkable economy 
of 12.66 lbs. of steam per E. H. P. per hour. 

A 1,500 K. W. Westinghouse-Parsons turbine, using 
dry saturated steam of 150 lbs. pressure with 27 in. 
vacuum, consumed 14.8 lbs. steam per E. H. P. houi 
at full load, and 17.2 lbs. at one-half load. 



CHAPTER V 

THE CURTIS STEAM TURBINE 

The Curtis turbine an impulse and reaction machine — Admission 
of the steam — System of expanding nozzles — Ratio of expan- 
sion in four stage machine — Step bearing — Method of lubri- 
cation — Action of the steam in a two stage machine — Static 
force, and force of velocity compared — Speed regulation in 
Curtis turbine — Accomplished in first group of nozzles — How 
admission of steam is controlled — Velocity of the steam is 
constant, with light or full load — Two main sources of econ- 
omy in the steam turbine — Efficiency tests of Curtis turbine. 

In the Curtis turbine the heat energy in the steam is 
imparted to the wheel, both by impulse and reaction, 
but the method of admission differs from that of the 
VVestinghouse-Parsons in that the steam is admitted 
through expanding nozzles in which nearly all of the 
expansive force of the steam is transformed into the 
force of velocity. The steam is caused to pass through 
one, tw^o, or more stages of moving elements, each 
stage having its own set of expanding nozzles, each 
succeeding set of nozzles being greater in number and 
of larger area than the preceding set. The ratio of 
expansion within these nozzles depends upon the 
number of stages, as, for instance, in a two-stage 
machine the steam enters the initial set of nozzles at 
boiler pressure, say i8o lbs. It leaves these nozzles 
and enters the first set of moving blades at a pressure 
of about 15 lbs., from which it further expands to 
atmospheric pressure in passing through the wheels 
and intermediates. From the pressure in the first 
stage the steam again expands through the larger area 

370 



THE CURTIS STEAM TURBINE 371 

of the second stage nozzles to a pressure slightly 
greater than the condenser vacuum at the entrance to 
the second set of moving blades, against which it now 
impinges and passes through still doing v^ork, due to 
velocity and mass. 

From this stage the steam passes to the condenser. 
If the turbine is a four-stage machine and the initial 
pressure is 180 lbs., the pressure at the different stages 
would be distributed in about the following manner: 
Initial pressure, 180 lbs.; first stage, 50 lbs.; second 
stage, 5 lbs.; third stage, partial vacuum, and fourth 
stage, condenser vacuum. 

The Curtis turbine is built by the General Electric 
Co. at their works in Schenectady, New York, and 
Lynn, Mass. The larger sizes are of the vertical type, 
and those of small capacity are horizontal. 

Fig- 134 gives a general view of a 5,000 K. W. 
turbine and generator. The generator is shown at the 
top, while the turbine occupies the middle and lower 
section. A portion of the inlet steam pipe is shown, 
ending in one nozzle group at the side. There are 
three groups of initial nozzles, two of which are not 
shown. The revolving parts of this unit are set upon 
a vertical shaft, the diameter of the shaft correspond- 
ing to the. size of the unit. For a machine having the 
capacity of the one illustrated by Fig. 134 the diameter 
of the shaft is 14 in. 

The shaft is supported by and runs upon a step 
bearing at the bottom. This step bearing consists of 
two cylindrical cast iron plates, bearing upon each 
other and having a central recess between them into 
which lubricating oil is forced under pressure by a 
steam or electrically driven pump, the oil passing up 
from beneath. A weighted accumulator is sometimes 



372 



ENGINEERING 



installed in connection with the oil pipe as a con- 
venient device for governing the step bearing pumps,^ 
and also as a safety device in case the pumps should 
fail, but it is seldom required for the latter purpose, as 




FIGURE 134. 

5,000 K.W. CURTIS STEAM TURBINE DIRECT CONNECTED TO 5,000 

K.W. THREE-PHASE ALTERNATING CURRENT GENERATOR. 

the step bearing pumps have proven, after a long 
service in a number of cases, to be reliable. The 
vertical shaft is also held in place and kept steady by 
three sleeve bearings, one just above the step, one 
between the turbine and generator, and the other near 



THE CURTIS STEAM TURBINE 



37S 



the top. These guide bearings are lubricated by a 
standard gravity feed system. It is apparent that the 
amount of friction in the machine is very small, and 
as there is no end thrust caused by the action of the 
steam, the relation between the revolving and station- 
ary blades may be maintained accurately. As a con- 




FIGURE 135. 
500 K.W. CURTIS STEAM TURBINE IN COURSE OF CONSTRUCTION. 

sequence, therefore, the clearances are reduced to the 
minimum. 

The Curtis turbine is divided into two or more stages, 
and each stage has one, two or more sets of revolving 
blades bolted upon the peripheries of wheels keyed to 
the shaft. There are also the corresponding sets of 
stationary blades, bolted to the inner walls of the 
cylinder or casing. As in the Westinghouse-Parsons 



374 



ENGIXKERING 



type, the function of the stationary blades is to give 
direction to the flow of steam. 

Fig. 135 illustrates one stage of a 500 K. W. turbine 
in course of construction. It will be observed that 
there are three wheels, and that in the spaces between 
these wheels the stationary buckets or vanes are 




REVOLVTXG BUCKETS FOR CURTIS STE\M TUKBTNE. 







STATIONARY BUCKETS FOR CURTIS STEAM TUiiBliNE. 
FIGURE 136. 

placed, being firmly bolted to the casing. Fig. 136 
shows sections of both revolving and stationary 
buckets ready to be placed in position. The illustration 
in Fig. 135 shows the lower or last stage. The clear- 
ance between the revolving and stationary blades is 
from -^^ to yV i^-» ^^^s reducing the wastage of steam 
to a very low percentage. The diameters of the 



THE CURTIS STEAM TURBINE 375 

wheels vary according to the size of the turbine, that 
of a 5,000 K. W. machine being 13 ft. 

Fig. 137 shows a nozzle diaphragm with its various 
openings, and it will be noted that the nozzles are set 
at an angle to the plane of revolution of the wheel. 

Fig. 138 is a diagram of the nozzles, moving blades 
and stationary blades of a two-stage Curtis steam 
turbine. The steam enters the nozzle openings at the 
top, controlled by the valves shown, the regulation of 
which will be explained later on. In the cut Fig. 138 
two of the valves are open, and the course of the 
steam through the first stage is indicated by the arrows. 




FIGURE 137. NOZZLE. 

After passing successively through the different sets of 
moving blades and stationary blades in the first stage, 
the steam passes into the second steam chest. The 
flow of steam from this chamber to the second stage 
of buckets is also controlled by valves, but the function 
of these valves is not in the line of speed regulation 
but for the purpose of limiting the pressure in the stage 
chambers, in a manner somewhat similar to the control 
of the receiver pressure in a two-cylinder or three- 
cylinder compound reciprocating engine. 

The valves controlling the admission of steam to the 
second and later stages differ from those in the first 
group in that they partake more of the nature of slide 



376 



F.NUINEERING 



valves and may ue operated either by hand or auto- 
matically; in fact, they require but very little regulation, 



Stz^orr-y CT/^sst. 



m§ 



w. 



"I 




mu. 



^^^mLiiiiiiii^M 



maiaiiaaaaa^ 






^OZZ^ /D/arAD/-»f>ar^rn 




Ato\^rr>^ jB/Gic/<s^ 






mmmssmssssmL 






mnmmnmnnnmn 
I I I I i 1 

FIGURE 138. 
DIAGRAM OF NOZZLES AND BUCKETS IN CURTIS STjs iM TURBINE, 

as the governing is always done by the live steam 
admission valves. 

Action of the Steam in a Two-stage Machine. As 
previously stated, the steam first strikes the moving 
blades in the first stage of a two-stage machine at a 



THE CURTIS STEAM TURBINE 377 

pressure of about 15 lbs. above atmospheric pressure, 
but with great velocity. From this wheel it passes to 
the set of stationary blades between it and the next 
lower wheel. These stationary blades change the 
direction of flow of the steam and cause it to impinge 
the buckets of the second wheel at the proper angle. 

This cycle is repeated until the steam passes from 
the first stage into the receiving chamber or steam 
chest for the second stage. Its passage from this 
chamber into the second stage is controlled by valves, 
which, as before stated, are regulated either by hand 
or automatically. The course of the steam through 
the nozzles and blades of the second stage is clearly 
indicated by the arrows, and it will be noted that 
steam is passing through all the nozzles. 

At this point it might be well to consider the ques- 
tion which no doubt arises in the mind of the student 
in his efforts to grasp the underlying principles in the 
action of the steam turbine. Why is it that the 
impingement of the steam, at so low a pressure, against 
the blades or buckets of the turbine, imparts such a 
large amount of energy to the shaft? 

The answer is, because of velocity, and a good 
example of the manner in which velocity may be 
made to increase the capacity of an agent to do work 
is illustrated in the following way: Suppose that a 
man is standing within arm's length of a heavy plate 
glass window and that he holds in his hand an iron 
ball weighing 10 lbs. Suppose the man should place 
the ball against the glass and press the same there with 
all the energy he is capable of exerting. He would 
make very little, if any, impression upon the glass. 
Biit suppose that he should walk away from the 
window a distance of 20 ft. and then exert the same 



378 ENGINEERING 

amount of energy in throwing the ball against the 
glass, a different result would ensue. The velocity 
with which the ball would impinge the surface of the 
glass would no doubt ruin the window. Now, not- 
withstanding the fact that weight, energy and time 
involved were exactly the same in both instances, yet 
a much larger amount of work was performed in the 
latter case, owing to the added force imparted to the 
ball by the velocity with which it impinged against 
the glass. 

Speed Regulation. The governing of speed is 
accomplished in the first set of nozzles, and the control 
of the admission valves here is effected by means of 
a centrifugal governor attached to the top end of the 
shaft. This governor, by a very slight movement, 
imparts motion to levers, which in turn work the valve 
mechanism. The admission of steam to the nozzles 
is controlled by piston valves, which are actuated by 
steam from small pilot valves which are in turn under 
the control of the govert^or. Fig. 139 shows the form 
of governor for a 5,000 K. W. turbine, and Fig. 140 
shows the electrically operated admission valves for 
one set of nozzles. 

Speed regulation is effected by varying the number 
of nozzles in flow, that is, for light loads fewer nozzles 
are open and a smaller volume of steam is admitted to 
^he turbine wheel, but the steam that is admitted 
impinges the moving blades with the same velocity 
always, no matter whether the volume be large or 
small. With a full lof^d and all the nozzle sections in 
flow, the steam passes to the wheel in a broad belt and 
steady flow. 

The Curtis Steam Turbine is the result of the investi- 
g:ations and experiments of Mr. C. G. Curtis of New 



THE CURTIS STEAM TURBINE 379 

York, and while retaining the advantage of the expand- 
ing nozzle of De Laval, it at the same time utilizes the 
energy acquired by velocity, by causing the steam to 




FIGURE 139. GOVERNOR FOR 5,000 K.W. TURBINE. 

impinge the moving buckets of two or more wheels in 
succession. A portion of this velocity force is given 
up in the first stage, and another portion in the second 
stage, and this process is repeated, the steam in each 



380 



ENGINEERING 



case being first caused to expand in divergent nozzles 
and thus acquire new velocity before it is allowed to 
impinge the moving blades of the next lower stage. The 
pressure in each succeeding stage of expansion becomes 
lower and lower, until finally vacuum is reached. 

As previously stated, two of the main sources of 
economy that the steam turbine possesses in a much| 
higher degree than does the reciprocating engine are:} 

first, its adaptability 
for using super- 
heated steam, anc 
second, the possibil- 
ity of maintaining a 
higher degree of 
vacuum. 

The efficiency 
. shown by the steam 
' turbine is certainly 
remarkable, and one 
peculiar feature re- 
garding the machine 
is, that its efficiency 
is not affected by 
variations in load to the same degree as is the efficiency 
of the reciprocating engine. 

A 600 K, W. Curtis turbine operating at 1,50a 
R P. M., with steam at 140 lbs. gauge pressure and 
28.5 in. vacuum, showed a steam consumption as fo^ 
.ows, steam superheated 150"^: 
At full load, 12.5 lbs. per E. H. P. per hour. 
At half load, 13.25 lbs. per E. H. P. per hour. 
At one-sixth load, 16.2 lbs. per E. H. P. per hour. 
And at one-third overload, 12.4 lbs. per E. H. P. per 
hour. 




FIGURE 140. ELECTRICALLY OPER- 
ATED VALVE. 



I 



THE CURTIS STEAM TURBINE 381 

This would seem to indicate that the efficiency of 
the steam turbine increases with overload, at least up 
to a certain point. 

In another test of a Curtis turbine, using dry 
saturated steam of 145 lbs. gauge pressure, the steam 
consumption at full load was 14.76 lbs. per E. H. P. 
hour, and at half load the rate was 15.95 lbs. per 
E. H. P. hour. The same machine using steam super- 
heated 150° showed a steam consumption of 
13.27 lbs. per E. H. P.hour, at full load. 

A Curtis turbine carrying a commercial load on a 15- 
hour run showed an average coal consumption as 
follows; the turbine was operated with one boiler 
independently of the other boilers in the battery, and 
the steam was not superheated: Coal consumed per 
E. H. P. hour, 1.86 lbs. 

The highest type of modern reciprocating engine, 
triple expansion, condensing, having steam jacketed 
cylinders, shows a coal consumption of 1.5 to 2 lbs. per 
H. P. per hour, assuming the evaporation to be 8 lbs. 
water per pound of coal. 



CHAPTER VI 
THE HAMILTON-HOLZWARTH STEAM TURBINE 

The Hamilton-Holzwarth steam turbine — Points of difference 
between it and the Westinghouse- Par sons — Small clearances 
necessary — Stationary discs and guide vanes — Running 
wheels— Expansion of the steam and where it occurs — Action 
of the steam within the machine — Various stages in high ana 
low pressure casings — Curvature of vanes — Purpose of sta- 
tionary discs — Thrust ball bearings — Description of the gov- 
ernor and regulating mechanism — Close regulation — Method 
of changing speed while running. 

This turbine resembles the Westinghouse-Parsons 
turbine in some respects, prominent of which is that 
it is a full stroke turbine, that is, that the steam flows 
through it in one continuous belt or veil in screw line, 
the general direction being parallel with the shaft. 
But, unlike the Parsons type, the steam in the Hamil- 
ton-Holzwarth turbine is made to do its work only by 
impulse, and not by impulse and reaction combined. 
It might thus be termed an action turbine. 

The Hamilton-Holzwarth steam turbine is based 
upon and has been developed from the designs of Prof. 
Rateau, and is being manufactured in this country by 
the Hooven-Owens-Rentschler Co. of Hamilton, Ohio. 
It is horizontal and placed upon a rigid bed plate 
of the box pattern. All steam, oil and water pipes 
are within and beneath this bed plate, as are also 
the steam inlet valve and the regulating and by-pass 
valves. 

The smaller sizes of this turbine are built in a single 
casing or cylinder, but for units of 750 kilowatts and 

382 



THE HAMILTON-HOLZWARTH STEAM TURBINE 383 

larger the revolving element is divided into two parts, 
high and low pressure. 

There are no balancing pistons in this machine, the 
axial thrust of the shaft being taken up by a thrust 
ball-bearing The interior of the cylinder is divided 
into a series of stages by stationary discs which are set 
in grooves in the cylinder and are bored in the center 
to allow the shaft, or rather the hubs of the running 
wheels that are keyed to the shaft, to revolve in this 
bore. 

The clearance allowed is as small as practical, as it 
is in this clearance between the revolving hub and the 
circumference of the bore of the stationary disc that 
the leakage losses occur. It should be noted that 
between each two stationary discs there is located a 
running wheel, and that the clearance between the run- 
ning vanes and the stationary vanes is made as slight 
as is consistent with safe practice; otherwise leakage 
would occur here also, and besides this there would be 
a distortion of the steam jet and entrainment of the 
surrounding atmosphere, resulting in a rapid decline in 
economy if the clearance between the stationary and 
moving elements was not reduced to as small a fraction 
as possible. 

As before stated, the stationary discs are firmly 
secured to the interior walls of the casing. At intervals 
on the outside periphery of these discs are located the 
stationary or guide vanes. These are made of drop 
•forged steel. They are set in a groove on the outside 
edge of the disc and fastened with rivets. Both disc 
and vanes are then ground, giving the vanes the profile 
that they should have for the most efficient expansion 
of the steam. After this is done a steel ring is shrunk 
on the outside periphery of the vanes and the steam 



384 ENGINEERING 

channels in the disc. These discs are then placed in 
the grooves in the casing at regular intervals, and in 
the spaces between them are the running wheels. 

The casing is divided into an upper and lower half. 
The running wheels are built with a cast steel hub 
having a steel disc riveted on to each side, thus forming 
a circumferential ring space into which the running 
vanes are riveted. A thin steel band or rim is tied on 
the outer edge of the vanes, thus forming an outer wall 
to the steam channels and confining the steam within 
the vanes. These vanes are also milled on both edges, 
on the influx and efflux side of the wheel, thus forming 
them to the shape corresponding to the theoretical 
diagram. 

The running vanes conform in section somewhat to 
the Parsons type, but the action of the steam upon 
them and also within the stationary vanes is different. 
The expansion of the steam and consequent develop- 
ment of velocity takes place entirely within the station- 
ary vanes, which also change the direction of flow of 
the steam and distribute it in the proper manner to the 
vanes of the running wheels, which, according to the 
claims of the makers, the steam enters and leaves at 
the same pressure, thus allowing the wheel to revolve 
in a uniform pressure. 

Fig. 141 shows a general view of the Hamilton- 
Holzwarth turbine, and the action of the steam within 
the machine may be described as follows: After leaving 
the steam separator that is located beneath the bed. 
plate, the steam passes through the inlet or throttle 
valve, the stem of which extends up through the floor 
near the high pressure casing and is protected by a 
floor stand and equipped with a hand wheel, shown in 
Fig. 141. The steam now passes through the regulat- 



THE HAMILTON-HOLZWARTH STEAM TURBINE 



385 



ing valve, which will be described later on. From this 
valve it is led throui^h a curved pjpe to the front head 

of the high pressure cas- 
ing or cylinder. In this 
head is a ring channel 
into which the steam 
enters, and from whence 
it flows through the first 
set of stationary vanes. 
In these vanes the first 
stageof expansionoccurs, 
the velocity of the flow 
is accelerated, and the 
direction of flow is 
. changed by the curve of 
^ the vanes in such man- 
? ner that the steam im- 




o pinges the vanes of the 
^ first running wheel at the 
proper angle and in a full 
cylindrical belt, impart- 
ing b}^ impulse a portion 
of its energy to the wheel. 
Passing through the 
vanes of this wheel, the 
steam immediately enters 
the vanes of the second 
stationary disc, which are 
larger in area than those 
of the first, and here 
occurs the second stage 
of expansion, another acceleration of velocity, and also 
the proper change in direction, and the steam leaves 
this distributer and impinges the vanes of the second 



386 ENGINEERING 

running wheel. This cycle is repeated throughout the 
several stages of the turbine, a certain percentage of 
the heat energy in the steam being imparted by impulse 
to each wheel and thence to the turbine shaft. From 
the last running wheel the steam is led through re- 
ceiver pipes to the front head of the low-pressure 
cylinder, or, if there is but one cylinder, directly to 
the condenser or the atmosphere. 

In the low-pressure casing, which is larger in diam- 
eter than the high-pressure the steam is distributed in 
the same manner as it is in the high-pressure casing. 
There is, however, in the front head of the low-pres- 
sure casing an additional nozzle through which live 
steam may be admitted in case of overload. The 
design of this nozzle is such that the live steam entering 
and passing through it and controlled by the governor 
exerts no back pressure on the steam coming from the 
receiver, but, on the contrary, its action is similar to 
the action of an injector, that is, it tends to suck the 
low-pressure steam through the first set of stationary 
vanes of the low-pressure turbine. 

The first stationary disc of the low-pressure turbine 
has guide vanes all around its circumference, so that 
the steam enters the turbine in a full cylindrical belt, 
interrupted only by the guide vanes. To provide for 
the increasing volume as the steam expands in its 
course through the turbine, the areas of the passages 
through the distributers and running vanes must be 
progressively enlarged. The gradual increase in the 
dimensions of the stationary vanes permits the steam 
to expand within them, thus tending to maintain its 
velocity, while at the same time the vanes guide the 
steam under such a small angle that the force with 
which it impinges the vanes of the next running wheel 



THE HAMILTON-HOLZWARTH STEAM TURBINE 387 

is as effective as possible. The curvature of the vanes 
is such that the steam while passing through them will 
increase its velocity in a ratio corresponding to its 
operation. 

The purpose of the stationary discs is, as has been 
stated, to distribute the steam to the running wheels. 
They also take the back pressure of the steam as it 
impinges the vanes of the running wheels, thus in a 
sense acting as balancing pistons. 

In all steam turbines one of the main requisites for a 
quiet-running machine is that the revolving element 
or rotor shall be perfectly balanced. The rotary body 
of the Hamilton-Holzwarth turbine consists of a plu- 
rality of running wheels, each one of which is balanced 
by itself before being placed upon the shaft. All the 
bearings are lubricated in a thorough manner by oil 
forced up into the bottom bushing or shell under slight 
pressure. Flexible couplings are used between the 
high and low-pressure shafts, and for connecting the 
turbine shaft to the generator shaft or other shaft to be 
driven. By means of the thrust ball-bearing on the 
exhaust end of the turbine the shaft may be adjusted 
in an axial direction in such manner as to accurately 
preserve the desired position of the running wheels 
with relation to the stationary discs. 

The governor is of the spring and weight type, 
adapted to high speed, and is designed especially for 
turbine governing. It is directly driven by the turbine 
shaft, revolving with the same angular velocity. Its 
action is as follows: Two discs keyed to the shaft 
drive, by means of rollers, two weights sliding along a 
cross bar placed at right angles through the shaft and 
compressing two springs against two nuts on the cross 
bar. Every movement of the weights, caused by 



388 ENGINEERING 

increasing or decreasing the angular velocity of the 
turbine shaft, is transmitted by means of levers to 
a sleeve which actuates the regulating mechanism. 
These levers are balanced so that no back pressure is 
exerted upon the weights. The whole governor is 
closed in by the discs, one on each side, and a steel 
ring secured by concentric recesses to the discs. In 
order to decrease the friction within the governor and 
regulating mechanism, thrust ball-bearings and friction- 
less roller-bearings are used. 

As previously stated, the regulating valve is located 
beneath the bed plate. One side of it is connected by 
a curved pipe with the front head of the high-pressure 
cylinder and the other side is connected with the inlet 
valve. The regulating valve is of the double-seated 
poppet valve type. Valves and valve seats are made 
of tough cast steel, to avoid corrosion as much as 
possible, and the valve body is made of cast iron. 

Immediately below the regulating valve and forming 
a part of it in one steam chamber is located the by- 
pass regulating valve. Thus the use of a second 
stuffing box for the stem of this valve is avoided. 
The function of this valve is to control the volume of 
the live steam supply that flows directly to the by-pass 
nozzles in the front head of the low-pressure casing. 
This valve is also a double-seated poppet valve. 

The main regulating valve is not actuated directly by 
the governor, but by means of the regulating mechan- 
ism. The construction and operation of this regulat- 
ing mechanism is as follows: The stem of the 
regulating valve is driven by means of bevel gears by 
a shaft that is supported in frictionless roller-bearings. 
On this shaft there is a friction wheel that the governor 
can slide across the face of a continuously revolving 



THE HAMILTON-HOLZWARTH STEAM TURBINE 389 

friction disc by means of its sleeve and bell crank 
lever. This revolving disc is keyed to a solid shaft 
which is driven by a coupling from a hollow shaft. 
This hollow shaft is driven by the turbine shaft through 
the medium of a worm gear. The solid shaft, with the 
continuously revolving friction disc, can be slightly 
shifted by the governor sleeve so that the two friction 
discs come into contact when the sleeve moves, that 
is, when the angular velocity changes. If this change 
is relatively great, the sleeve will draw the periodically 
revolving friction disc far from the center of the always 
revolving one, and this disc will quickly drive the 
stem of the regulating valve and the flow of steam will 
thus be regulated. As soon as the angular velocity 
falls below a certain percentage of the normal speed, 
the driving friction disc is drawn back by the governor, 
the regulating valve remains open and the whole regu- 
lating mechanism rests or stops, although the shaft is 
still running. 

Should the angular velocity of the shaft reach a pomt 
2.5 per cent higher than normal, the governor will shut 
down the turbine. If an accident should happen to 
the governor, due to imperfect material or breaking or 
weakening of the springs, the result would be a shut- 
down of the turbine. 

In order to change the speed of the turbine while 
running, which might be necessary in order to run the 
machine parallel with another prime mover, a spring 
balance is provided, attached to the bell crank lever 
of the regulating mechanism. The hand wheel of this 
spring balance is outside of the pedestal for regulating 
mechanism and near the floor-stand and hand wheel. 
With this spring balance the speed of the turbine may 
be changed 5 per cent either way from normal. 



390 ENGINEERING 

All the bearings of the unit are thoroughly lubricated 
with oil forced under pressure by the oil pump driven 
by means of worm gearing by the turbine itself. After 
flowing through the bearings the oil is passed through 
a filter and from thence to the oil tank located within 
the bed plate, from whence it is taken by the oil pump. 
All revolving parts are enclosed, and the principal 
part of the regulating mechanism operates in a bath 
of oil. 



CHAPTER VII 

DE LAVAL STEAM TURBINE 

De Laval steam turbine — High velocity — The De Laval divergent 
nozzle — Adiabatic expansion of steam within nozzle — Conver- 
sion of static energy into kinetic — Form of De Laval wheel — 
Speed of buckets — Speed of turbine shaft, and how it is 
reduced — Construction of the wheel — Number of buckets 
required — Number of nozzles — Gear and flexible shaft — 
Description of governor — Vacuum valve — Operation of gov- 
ernor — Efficiency tests — Steam consumption— Cross section 
of wheel showing correct design— Table of sizes, giving speed 
and weight. 

The De Laval steam turbine, the invention of Carl 
De Laval of Sweden, is noted for the simplicity of its 
construction and the high speed of the wheel —10,000 
to 30,000 R. P. M. The difficulties attending such 
high velocities are, however, overcome by the long, 
flexible shaft and the ball and socket type of bearings, 
which allow of a slight flexure of the shaft in order 
that the wheel may revolve about its center of gravity, 
rather than the geometrical center or center of position. 
All high speed parts of the machine are made of forged 
nickel steel of great tensile strength. But one of the 
most striking features of this turbine is the diverging 
nozzle, also the invention of De Laval. 

It is well known that in a correctly designed nozzle 
the adiabatic expansion of the steam from maximum 
to minimum pressure will convert the entire static 
energy of the steam into kinetic. Theoretically this is 
what occurs in the De Laval nozzle. The expanding 
steam acquires great velocity, and the energy of the jet 

391 



392 



ENGINEERING 



of steam issuing from the nozzle is equal to the amount 
of energy that would be developed if an equal volume 
of steam were allowed to adiabatically expand behind 
the piston of a reciprocating engine, a condition, how- 




ever, which for obvious reasons has never yet been 
attained in practice with the reciprocating engine. 
But with the divergfent nozzle the conditions are 
different. 
Referring to Fig. 142, a continuous volume of steam 



DE LAVAL STEAM TURBINE 



393 



at maximum pressure is entering the nozzle at E, and, 
passing through it, expands to minimum pressure at F, 
the temperature of the nozzle being at the same time 
constant and equal to the temperature of the passing 
steam. The principles of the De Laval expanding 
nozzle are in fact more or less prominent in all steam 




FIGURE 143. THE DE LAVAL TURBINE WHEEL AND NOZZLES. 



turbines. The facilities for converting heat into work 
are increased by its use, and the losses by radiation 
and cooling influences are greatly lessened. 

The De Laval steam turbine is termed by its builders 
a high-speed rotary steam engine. It has but a single 
wheel, fitted with vanes or buckets of such curvature as 



391 



EXGIXEERIXG 



has been found to be best adapted for receiving the 
impulse of the steam jet. There are no stationary or 




m 

-:--:^ *-...■-■ i 



guide blades, the angular position of the nozzles giving 
direction to the jet. Fig. 143 shows the form of wheel 



DE LAVAL STEAM TURBINE 395 

and the nozzles. The nozzles are placed at an angle of 
20° to the plane of motion of the buckets, and the 
course of the steam is shown by the illustration. 

The heat energy in the steam is practically devoted 
to the production of velocity in the expanding or 
divergent nozzle, and the velocity thus attained by the 
issuing jet of steam is about 4,000 ft. per second. To 
attain the maximum of efificiency the buckets attached 
to the periphery of the wheel against which this jet 
impinges should have a speed of about 1,900 ft, per 
second, but, owing to the difificulty of producing a 
material for the wheel strong enough to withstand the 
strains induced by such a high speed, it has been found 
necessary to limit the peripheral speed to 1,200 or 
1,300 ft. per second. 

Fig. 144 shows a De Laval steam turbine motor of 
300 H. P., which is the largest size built up to the 
present time, its use having been confined chiefly to 
light work. 

The turbine illustrated in Fig. 144 is shown directly 
connected to a 200 K. W. two-phase alternator. The 
steam and exhaust connections are plainly shown, as 
also the nozzle valves projecting from the turbine 
casing. The speed of the turbine wheel and shaft is 
entirely too high for most practical purposes, and it is 
reduced by a pair of very perfectly cut spiral gears, 
usually made 10 to I. These gear wheels are made of 
solid cast steel, or of cast iron with steel rims pressed 
on. The teeth in two rows are set at an angle of 90° to 
each other. This arrangement insures smooth running 
and at the same time checks any tendency of the shaft 
towards end thrust, thus dispensing with a thrust 
bearing. 

The working parts of the machine are clearly illus- 



396 



ENGINEERING 




FIGURE 145. 



trated in Fig. 145, and a fairly good conception of the 
assembling of the various members, and especially the 
reducing gears, may be had by reference to Fig. 146, 



DE LAVAL STEAM TURBINE 397 

which shows a no H. P. turbine and rotary pump with 
the upper half of the gear case and field frame removed 
for purposes of inspection. The slender shaft is seen 
projecting from the center of the turbine case, and upon 
this shaft are shown the small pinions meshing into the 
large spiral gears upon the two pump shafts. 

Referring to Fig. 145, A is the turbine shaft, B is the 
turbine wheel, and C is the pinion. As the turbine 
wheel is by far the most important element, it will be 
taken up first. It is made of forged nickel steel, and 
it is claimed by the builders, the De Laval Steam 
Turbine Co. of Trenton, New Jersey, that it will with- 
stand more than double the normal speed before 
showing any signs of distress. A clear idea of the 
construction of the wheel and buckets may be had by 
reference to Fig. 143. The number of buckets varies 
according to the capacity of the machine. There are 
about 350 buckets on a 300 H. P. wheel. The buckets 
are drop forged and made with a bulb shank fitted in 
sFots milled in the rim of the wheel. 

Fig. 147 is a sectional plan of a 30 H. P. turbine con- 
nected to a single dynamo, and Fig. 148 is a sectional 
elevation of the same. 

The steam, after passing the governor valve C, Fig. 
148, enters the steam chamber D, Fig. 147, from 
whence it is distributed to the various nozzles. The 
number of these nozzles depends upon the size of the 
machine, ranging from one to fifteen. They are 
generally fitted with shut-off valves (see Fig. 144) by 
which one or more nozzles can be cut out when the 
load is light. This renders it possible to use steam at 
boiler pressure, no matter how small the volume 
required for the load. This is a matter of great 
importance, especially where the load varies con- 



398 



ENGINEERING 




siderably, as, for instance, there are plants in which 
during certain hours of the day a 300 H. P. machine 
may be taxed to its utmost capacity and during certain 



DE LAVAL STEAM TURBINE 



399 




400 ENGINEERING ' 

otner hours the load on the same machine may drop to 
50 H. P. In such cases the number of nozzles in action 
may be reduced by closing the shut-off valves until the 
required volume of steam is admitted to the wheel. 
This adds to the economy of the machine. After pass- 
ing through the nozzles, the steam, as elsewhere 
explained, is now completely expanded, and in imping- 
ing on the buckets its kinetic energy is transferred to 
the turbine wheel. Leaving the buckets, the steam 
now passes into the exhaust chamber G, Fig. 147, and 
out through the exhaust opening H, Fig. 148, to the 
condenser or atmosphere as the case may be. 

The gear is mounted and enclosed in the gear case I, 
Fig. 147. J is the pinion made solid with the flexible 
shaft and engaging the gear wheel K. This latter is 
forced upon the shaft L, which, with couplings M, 
connects to the dynamo or is extended for other 
transmission. 

O, Fig. 148, is the governor held with a taper shank 
in the end of the shaft L, and by means of the bell 
crank P operates the governor valve C. The flexible 
shaft is supported in three bearings, Fig. 147. Q and 
R are the pinion bearings and S is the main shaft bear- 
ing which carries the greater part of the weight of the 
wheel. This bearing is self-aligning, being held to its 
seat by the spring and cap shown. 

T, Fig. 147, is the flexible bearing, being entirely 
free to oscillate with the shaft. Its only purpose is o 
prevent the escape of steam when running non-coa 
densing, or the admission of air to the wheel case when 
running condensing. The flexible shaft is made very 
slender, as will be observed by comparing its size with 
that of the rotary pump shaft in Fig. 146. It is by means 
of this slender, flexible shaft that the dangerous feature 



DE LAVAL STEAM TUKBINB 



401 




4«r^ 



ENGINEERING 



of the enormously high speed of this turbine is 
eliminated. 

The governor is of the centrifugal type, although 
differing greatly in detail from the ordinary fly ball 
governor, as will be seen by reference to Fig. 149. It 
is connected directly to the end of the gear wheel shaft. 
Two weights B are pivoted on knife edges A with 




FIGURE 14G. 



hardened pins C, bearing on the spring seat D. E is 
the governor body fitted in the end of the gear wheel 
shaft K and has seats milled for the knife edges A. It 
is afterwards reduced in diameter to pass inside of the 
weights and its outer end is threaded to receive the 
; djusting nut I, by means of which the tension of the 
spring, and through this the speed of the turbine, is 
adjusted. When the sp^ed accelerates, the weights. 



DE LAVAL STEAM TURBINE 403 

affected by centrifugal force, tend to spread apart, and 
pressing on the spring seat at D push the governor pin 
G to the right, thus actuating the bell crank L and 
cutting off a part of the flow of steam. 

It has been found necessary with this turbine, when 
running condensing, to introduce a valve termed a 
vacuum valve, also controlled by the governor, as it has 
been found that the governor valve alone is unable to 
hold the speed of the machine within the desired limit. 
The function of the vacuum valve is as follows: The 
governor pin G actuates the plunger H, which is 
screwed into the bell crank L, but without moving the 
plunger relative to said crank. This is on account of 
the spring M being stiffer than the spring N, whose 
function is to keep the governor valve open and the 
plunger H in contact with the governor pin. When 
a large portion of the load is suddenly thrown off, the 
governor opens, pushing the bell crank in the direction 
of the vacuum valve T. This closes the governor 
valve, which is entirely shut off when the bell crank is 
pushed so far that the screw O barely touches the 
vacuum valve stem J. Should this not check the speed 
sufficiently, the plunger H is pushed forward in the 
now stationary bell crank and the vacuum valve is 
opened, thus allowing the air to rush into the space P 
in which the turbine wheel revolves, and the speed is 
immediately checked. 

The main shaft and dynamo bearings are ring oiling. 
The high-speed bearings on the turbine shaft are fed 
by gravity from an oil reservoir, and the drip oil is 
collected in the base and maybe filtered and used over 
again. 

The fact that the steam is used in but a single stage 
or set of buckets and then allowed to pass into the 



404 



ENGINEERING 



exhaust chamber might appear at first thought to be a 
great loss of kinetic energy, but, as has been previously 
stated, the static energy in the steam as it enters the 
nozzles is converted into kinetic energy by its passage 
through the divergent nozzles, and the result is a 
greatly increased volume of steam leaving the nozzles 
at a tremendous velocity, but at a greatly reduced 




L23 



FIGURE 150o 



pressure — practically exhaust pressure — i m p i n g i n g 
against the buckets of the turbine wheel and thus causing 
it to revolve. 

Efficiency tests of the De Laval turbine show a high 
economy in steam consumption, as, for instance, a test 
made by Messrs. Dean and Main of Boston, Mass., on 
a 300 H. P. turbine, using saturated steam at about 
200 lbs. pressure per sq. in. and developing 333 Brake 



DE LAVAL STEAM TURBINE 



405 



H. P., showed a steam consumption of 15.17 lbs. per 
B< He P., and the same machine, when supplied with 
superheated steam and carrying a load of 352 B. H. P., 
consumed but 13.94 lbs. per B. H. P. These results 
compare most favorably with those of the highest type 
of reciprocating engines. 

Fig. 150 shows a cross section of a 300 H. P. De 
Laval wheel, showing the design necessary for with- 
standing the high centrifugal stress to which these 
wheels are subjected. All De Laval wheels are tested 
to withstand the centrifugal stress of twice their normal 
velocity without showing signs of fatigue. 

The following table gives the sizes and weights of 
some of these turbines, together with revolutions per 
minute of the turbine shaft and the main shaft. 



Horse Power 


Revol-utions 
Turbine Shaft 


Revolutions 
Main Shaft 


Approximate 
Weight 
Pounds 


5 

10 

20 

75 

110 

225 

300 


30,000 
24,000 
20,000 
16,400 
13,000 
11,060 
10,500 


3,000 
2,400 
2,000 
1,500 
1,200 
900 
900 


330 

650 

1,250 

5,000 

8,000 

15,000 

20,000 



CHAPTER VIII 

DISPOSAL OF THE EXHAUST STEAM OF STEAM 
TURBINES 

Advantages of exhausting into a condenser — Possible to maintain 
higher vacuum in condenser of a turbine than with reciprocat- 
ing engine — Surface condensers — Bulkley injector condenser 
— Steam turbine condensing apparatus at St. Louis Exposition, 
1904 — Dry air pump — Gain in economy from high vacuum — 
Cost of operating auxiliaries — Necessity of excluding all air 
from condensing system — Ways in which air may be en- 
trained — Comparative efficiency of turbines and reciprocating 
engines — Percentage of saving per each inch increase in 
vacuum above 25 inches — Advantages of superheating the 
steam — Outlook for future of steam turbines. 

As in the case of the reciprocating engine, the 
highest efficiency in the operation of the steam turbine 
is obtained by allowing the exhaust steam to pass into 
a condenser, and experience has demonstrated that it 
is possible to maintain a higher vacuum in the con- 
denser of a turbine than in that of a reciprocating 
engine. This is due, no doubt, to the fact that in the 
turbine the steam is expanded down to a much lower 
pressure than is possible with the reciprocating engine. 

The condensing apparatus used in connection with 
steam turbines may consist of any one of the modern 
improved systems, and as no cylinder oil is used within 
the cylinder of the turbine, the water of condensation 
may be returned to the boilers as feed water. If the 
condensing water is foul or contains matter that would 
be injurious to the boilers, a surface condenser should 
be used. If the water of condensation is not to be used 

406 



DISPOSAL OF THE EXHAUST STEAM 407 

in the boilers, the jet system may be employed. 
Another type of condenser that is being successfully 
used with steam turbines is the Bulkley injector 
condenser. 

Among the steam turbines that were on exhibition at 
the St. Louis exposition in 1904 the Westinghouse- 
Parsons and Lhe General Electric Curtis turbines were 
each equipped with Worthington surface condensers, 
fitted with improved auxiliary apparatus consisting of 
dry vacuum pumps, either horizontal of the well-known 
Worthington type, or rotative motor-driven, a hot well 
pump, and a pump for disposing of the condensed 
steam from the exhaust system. The two latter pumps 
were of the Worthington centrifugal type. The 
Hamilton-Holzwarth turbine was equipped with a 
Smith-Vaile surface condenser, fitted with a duplex 
double-acting air pump, a compound condensing 
circulating pump, and a rotative dry vacuum pump, 
motor-driven. The vacuum maintained was high, 28 
to 28.5 in. 

As an instance of the great gain in economy effected 
by the use of the condenser in connection with the 
steam turbine, a 750 K. W. Westinghouse-Parsons 
turbine, using steam of 150 lbs. pressure not super- 
heated and exhausting into a vacuum of 28 in., showed 
a steam consumption of 13.77 lbs. per B. H. P. per 
hour, while the same machine operating non-condensing 
consumed 28.26 lbs. of steam per B. H. P. hour. 
Practically the same percentage in economy effected by 
condensing the exhaust applies to the other types of 
steam turbines. 

With reference to the relative cost of operating the 
several auxiliaries necessary to a complete condensing 
outfit, the highest authorities on the subjeot place the 



408 ENGINEERING 

power consumption of these auxiliaries at from 2 to 7 
per cent of the total turbine output of power, A por- 
tion of this is regained by the use of an open heater 
for the feed water, into which the exhaust steam from 
the auxiliaries may pass, thus heating the feed water 
and returning a part of the heat to the boilers. 

A prime requisite to the maintenance of high vacuum, 
with the resultant economy in the operation of the 
condensing apparatus, is that all entrained air must be 
excluded from the condenser. There are various ways 
in which it is possible for air to find its way into the 
condensing system. For instance, there may be an 
improperly packed gland, or there may be slight leaks 
in the piping, or the air may be introduced with the 
condensing water. This air should be removed before 
it reaches the condenser, and it may be accomplished 
by means of the "dry'' air pump. 

This dry air pump is different from the ordinary air 
pump that is used in connection with most condensing 
systems. The dry air pump handles no water, the 
cylinder being lubricated with oil in the same manner 
as the steam cylinder. The clearances also are made 
as small as possible. These pumps are built either in 
one or two stages. 

A barometric or a jet condenser maybe used, or a 
surface condenser. The latter type lessens the danger 
of entrained air, besides rendering it possible to return 
the condensed steam, which is pure distilled water, to 
the boilers along with the feed water, a thing very much 
to be desired in localities where the water used for feed- 
ing the boilers is impregnated with carbonate of lime 
or other scale-forming ingredients. 

In comparing the efficiency of the reciprocating 
engine and the steam turbine it is not to be inferred 



DISPOSAL OF THE EXHAUST STEAM 409 

that reciprocating engines would not give better results 
at high vacuum than they do at the usual rate of 25 to 
26 in., but to reach and maintain the higher vacuum of 
28 to 28.5 in. with the reciprocating engine would 
necessitate much larger sizes of the low-pressure 
cylinder, as also the valves and exhaust pipes, in order 
to handle the greatly increased volume of steam at the 
low pressure demanded by high vacuum. 

The steam turbine expands its working steam to 
within I in. of the vacuum existing in the condenser, 
that is, if there is a vacuum of 28 in. in the condenser 
there will be 27 in. of vacuum in the exhaust end of 
the turbine cylinder. On the other hand, there is" 
usually a difference of 4 or 5 in. (2 to 2.5 lbs.) between 
the mean back pressure in the cylinder of a recipro- 
cating condensing engine and the absolute back pres- 
sure in the condenser. 

It therefore appears that the gain in economy per 
inch increase of vacuum above 25 in. is much larger 
with the turbine than it is with the reciprocating 
engine. Mr. J. R. Bibbins estimates this gain to be 
as follows: between 25 and 28 in. there is a gain of 3 J^ 
to 4 per cent per inch of increase, and at 28 in. 5 per 
cent. These results have been obtained by means of 
exhaustive tests conducted by Mr. Bibbins. Other 
high authorities on the steam turbine all agree as to the 
great advantages to be derived by incurring the extra 
expense of erecting a condensing plant that is capable 
of maintaining the high vacuum necessary to high 
efficiency. 

Another method by which the steam consumption of 
the turbine may be materially decreased and a great 
gain in economy effected is by superheating the steam. 
The amount of superheat usually specified is 100°, and 



410 ENGINEERING 

the apparatus employed for producing it maybe easily 
mounted in the path of the waste gases. The steam 
may thus be superheated without extra cost in fuel, and 
an increase of 8 to lo per cent in economy effected. 
The independent superheater requires extra fuel and 
labor, and the gain in this case is doubtful, but there 
can be no question as to the wisdom of utilizing the 
waste flue gases for superheating the steam. 

As previously stated, the steam turbine is peculiarly 
adapted for the use of highly superheated steam and 
high vacuum, and in these two particulars it excels the 
reciprocating engine At the present time many large 
plants are equipped with turbine engines that are giving 
the best of results, and the outlook for the future 
employment of this type of power producer is certainly 
very promising. 



CHAPTER IX. 



TPIE ALLIS-CHALMERS STEAM TURBINE. 

Since the publication of the first edition of this work, 
the AlHs-Chahners Company of Milwaukee, Wisconsin, 
have entered the field as manufacturers of steam turbines 
of the Parsons type. Fig. 151 shows a general view of 
the Allis-Chalmers steam turbine, and although it is 
essentially of the ''Parsons" type, still there are a num- 
ber of modifications in details of construction, as com- 
pared with the Westinghouse Parsons steam turbine,, 
some of which, no doubt may be considered as adding 
to the efficiency, and durability of the machine. 

Fig. 152 is a sectional view of the elementary "Par- 
sons" type of steam turbine and Fig. 153 shows a sec- 
tional view of the ''Parsons" turbine with the Allis-Chal- 
mers modifications. The action of the steam, and the 
general arrangement of the stationary and moving blades 
is practically the same in the two turbines, with the 
exception that, in the larger sizes of the Allis-Chalmers 
turbine the "balance" pistons for neutralizing the end 
thrust, are arranged in a different manner, the largest 
one of the three pistons, (piston N— Fig. 152) is replaced 
by a smaller balance piston. 

This piston presents the same effective area for the 
steam to act upon, as did the larger piston, for the reason 
that the working area of the latter in its original location 
consisted only of the annular area, included between its 
periphery, and the periphery of the next smaller piston^ 

411 



412 



ENGINEERING 




ALLIS-CHALMERS STEAM TURBINE 



413 



The pressure of the steam is brought to bear upon this 
equaHzing piston in its new position, by means of pas- 
sages or ports through the body of the rotor, connecting 
the third stage of the cylinder with the supplementary 
cylinder, in which the piston revolves. Fig. 154 shows 
the arrangement of blading, the course of the steam being 




B R 



CLEMENTARTMRSONGTYPE STEAM TURBINE 



FIGURE 152. 

Main bearings, A and B. Thrust bearing, R. Steam pipe, C. Main 
throttle valve, I), which is balanced, and operated by the governor. 
Steam enters ttie cylinder through passage E, passes to the left through 
^e alternate rows of stationary and revolving blades, leaving the cylin- 
der at F and passes into the condenser, or atmosphere through passage 
G. H, J and K are the three steps or stages of the machine. L, M 
and N are the three balance pistons. O, P and Q are the equalizing 
passages, connecting the balance pistons with the corresponding stages. 



indicated by the arrows. The clearances between the 
edges of the revolving and stationary blades, as shown in 
the cut, are relatively out of proportion to the actual 
clearances allowed. 

This clearance is preserved by means of a small thrust- 
bearing provided inside the housing of the main bearing. 

This thrust-bearing can be adjusted to locate and hold 
the rotor in such a position as will allow sufficient clear- 



414 



ENGINEERING 



ance to prevent actual contact between the moving and 
stationary blades and yet reduce the leakage of steam 
to a minimum. 




QBtaaurt fkasons tursk \vtth aoi&^haucrs hooficatk^ 



FIGURE 153. 

Sectional view of elementary Parsons steam turbine, with Allis 
Chalmers modifications. L and M are the two balance pistons at the 
high pressure end. Z is a smaller balance piston placed in the low 
pressure end, yet having the same effective area as did the larger piston 
N shown in Fig. 152. O and Q are the two equalizing passages for pis- 
tons L and M. Passage P is omitted in this construction and balance 
piston Z is equalized with the third stage pressure at Y. Valve V is 
a by-pass valve to allow of live steam being admitted to the second 
stage of the cylinder in case of a sudden overload. This by-pass valve 
is the equivalent of the by-pass valve used to admit live steam to the 
low pressure cylinder of a compound reciprocating engine. Valve V 
is arranged to be operated, either by the governor or by hand, as the 
conditions may require. Frictionless glands made tight by water pack- 
ing are provided at S and T where the shaft passes out of the cylinder. 
The shaft is extended at U and connected to the generator shaft by a 
flexible coupling. 



The method by v/hich the blades are fitted to and held 
in the rotor and cylinder of the Allis-Chalmers steam 
turbine is as follows : Each blade is individually formed 
by special machine tools, so that its root or foot is of 
an angular, or dove tail shape, and at its tip there is a 
projection. In order that the roots of the blades may 
be firmly held in position, a foundation ring, A Fig. 155, 



ALLIS-CHALMERS STEAM TURBINE 415 

IS provided, which after being formed to a circle of the 
proper diameter, has slots cut in it by a special milling 
machine. 







mrrrr 



MOVING 
BLADES 



STATfONARY 
BLADES 



MOVING 
BLADES 



STATIONARY 
BLADES 



MOVING 
BLADES 



STATIONARY 
BLADES 



FIGURE 154. 

Fig. 154 showing arrangement of blading and course of the steam 
jii Parsons steam turbine. 



These slots are formed of dove-tail shape to receive 
the roots of the blades and are at the same time accurate- 
ly spaced, and inclined so as to give the required pitch 
and angle to the blades. 



416 



ENGINEERING 



The foundation rings are also of dove-tail shape in 
cross-section, those holding the stationary blades are in- 
serted in dove-tail grooves in the cylinder and those hold- 
ing the revolving blades being pressed into the rotor or 
spindle. ^ 




FIGURE 155. 



The rings are firmly held in their places by key-pieces 
driven into place and upset into under-cut grooves, thus 
positively locking the whole structure together, and 
making it practically impossible for a blade to get out of 
place. 

The tips of the blades are held and firmlj bound to- 
gether by a shroud-ring, B. Fig. 155. 



ALLIS-CHALMERS STEAM TURBINE 



417 




FIGURE 156. 

SPINDLE OR ROTOR, ALLIS CHALMERS STEAM TURBINE. 

The rings which carry the blades are pressed on. 



418 ENGINEERING 

The shroud-rings are made channel-shape in cross-sec- 
tion, the flanges being made thin in order to prevent 
dangerous heating in case of accidental contact with 
either the walls of the cylinder or the surface of the 
rotor. 

I^ig*- 1 55 gives a clear idea of the construction and 
fitting of both the stationary and revolving blades. 

Fig. 156 shows the construction of the rotor of the 
Allis-Chalmers steam turbine. 

Fig. 157 shows an enlarged view^ of the blading as 
fitted in the turbine, the shroud-rings being clearly shown. 

The rings of blades are made up complete in half- 
rings in the shop ready for insertion in the turbine. 

Two of these half-rings are shown in figure 158, one 
with smaller blades, and one with larger blades for a 
turbine of moderate size. 

Fig. 159 illustrates the appearance of a number of 
rings of stationary blades inserted in the cylinder of an 
Allis-Chalmers steam turbine ; the cut having been made 
from an actual photograph and shows the mechanical 
accuracy of the work. 

The bearings of this turbine are of the self-adjusting 
ball and socket type, designed for high speed. Shims 
are provided for proper alignment. The lubrication of 
the four bearings, two for the turbine, and two for the 
generator, is accomplished by supplying an abundance 
of oil to the middle of each bearing and allowing it to 
flow out at the ends where it is caught, passed through 
a cooler, and pumped back to the bearings. 

The fact that the oil is supplied in large quantities 
to the bearings does not involve a heavy oil bill. 



ALLIS-CHALMERS STEAM TURBINE 419 




FIGURE 157. 

Fig. 157 illustrates blades as fitted in the rotor of Allis Chalmers 
steam turbine. The shroud ring protecting the tips of the blades is 
also shown. 



420 



ENGINEERING 




ALLIS-OHALMERS STEAM TURBINE 4^1 

The journals are practically floating- on films of oil, 
thus preventing that ''wearing out'' of the oil that oc- 
curs when it is suppHed in small ''doses." 



FIGURE 159. 
Shows a number of rows of stationary blades fitted in the 
cylinder of an Allis Chalmers steam turbine. 



As evidence of the economical use of oil the builders 
of this turbine cite the following examples : One 400 
K. W. turbine used only 50 g-allons of oil in six months. 



422 ENGINEERING 

In another installation of two i,ooo K. W. turbines 
only one-half gallon of oil was used per turbine a week. 

The governor is driven from the turbine-shaft by 
means of cut gears working in an oil-bath. 

The governor operates a balance throttle valve by 
means of a relay, except in very small sizes in which 
the valve is w^orked direct. 

In order to provide for any possible accidental de- 
rangement of the main governing mechanism, an en- 
tirely separate safety or over-speed governor is furnished. 
This governor is driven directly by the turbine shaft 
without the intervention of gearing, and is so arranged 
and adjusted that if the turbine should reach a prede- 
termined speed above that for which the main governor 
is set, the safety governor will come into action and trip 
a valve, shutting off the steam and stopping the turbine. 
A strainer is provided through which the steam is passed 
before admission to the turbine. 

It is no unusual thing for careless workmen to leave 
in steam pipes and valves such articles as bolts, nuts, 
pieces of gaskets, tools, etc. Should these find their 
way into a steam turbine they would damage the blading, 
perhaps seriously. To guard against such contingency, 
each Allis-Chalmers turbine is provided with a steam 
strainer, with perforations large enough not to obstruct 
the flow of steam, yet small enough to prevent the pas- 
sage of almost anything of such size as would damage 
the turbine blades. 

For connecting the rotors of the turbine and generator 
a special type of flexible coupling is used to provide for 
any slight inequality in the w^ar of the bearings, to per- 
mit axial adjustment of tlie turbine spindle, and to allow 
for differences in expansion. This coupling is so made 



ALLIS-CHALMERS STEAM TURBINE 423 

that it can be readily disconnected for the removal of 
the turbine spindle or of the revolving field of the gen- 
erator. Provision is made for ample lubrication of the 
adjoining faces of the coupling. The coupling is enclosed 
in the bearing housing, so that it is completely protected 
against damage, and cannot cause injury to the attend- 
ants. 

Waste of heat by radiation is prevented in the follow- 
ing manner: 

The hot parts of the turbine, up to the exhaust cham- 
ber, are covered with an ample thickness of non-conduct- 
ing material and lagged with planished steel. 

For large Allis-Chalmers turbines the bedplate is 
divided into two parts, one carrying the low-pressure end 
of the turbine and the bearings of the generator, the other 
carrying the high-pressure end of the turbine. The tur- 
bine is secured to the former, while the latter is pro- 
vided with guides which permit the machine to slide 
back and forth with differences of expansion caused by 
varying temperature, at the same time maintaining the 
alignment. 

It may be said in general of the steam turbine, that 
it has passed the experimental stage, and has come to the 
front as an efficient power producer, having a bright 
future before it. It has solved the problem of using 
superheated steam, owing to the absence of all rubbing 
parts exposed to the steam. This permits the use of 
steam of high temperature thus making it possible to 
realize the advantages of economical operation. 



CHAPTER X. 



REFRIGERATION. 



The process of refrigeration consists in the abstraction 
of heat from a substance, and if air, water, or ice is at 
hand at a lower temperature than it is desired to attain 
in the body or substance to be cooled the cooling element 
may be employed to perform the refrigeration directly 
without the aid of a machine. 

If a temperature of 32 degrees and not lower is de- 
sired ice can be used directly but if it is necessary to 
reach a temperature lower than 32 degrees a mixture of 
salt and ice or other freezing mixture must be used. 

By mixing one pound of calcium chloride with 0.7 lbs, 
of snow a solution is produced which will give a tempera- 
ture of 67° below zero. But freezing mixtures are toc^ 
expensive to be used for practical purposes, and it there- 
fore becomes necessary to employ machinery. 

The theory and practice of mechanical refrigeration 
are based upon the two first laws of thermo-dAmamics, 
that is to say first : that mechanical energy and heat are 
mutually convertible ; and second : that an external agent 
is necessary in order to complete or bring about the 
transformation. 

The generally accepted theory concerning the nature 
of heat together with definitions of the term.s, specific 
heat, latent heat, the mechanical equivalent of heat, etc., 
are fully discussed in Chapter 4 of this book and there- 
fore it will not be necessary to enlarge upon these sub- 

424 



REFRIGERATION 425 

jects in this connection except to state that the phrase 
commonly used, ''heat is generated by compression/' is 
somewhat misleading, because the amount of heat in the 
Universe is a fixed quantity, and the intrinsic energy' 
possessed by any gas is under given conditions a quantity 
that can be accurately calculated. Thus if a pound of 
air at a temperature of 70 degrees Fahrenheit, and at 
normal atmospheric pressure be taken as an example, the 
total quantity of energy it possesses is at once known. 
If this air be placed in a compressor and its volume be 
reduced to say one half of its original volume, and if 
this be done so rapidly that there is no time for heat to 
escape at the end of the compression, that is to say 
adiab'atically or instantaneous compression without trans- 
mission of heat, then its energy will have been increased 
by the amount of work done upon it. Its statical pres- 
sure will be increased, and its temperature will also have 
risen, by reason of its changed state or condition in- 
ternally. Now if the temperature be reduced to its for- 
mer amount, that is to say to 70 degrees Fahrenheit, its 
volume will contract, so that a small additional quantity 
of air will have to be forced in in order that the pressure 
may remain unchanged as the temperature is reduced. It 
will be seen that there will be now, consequently upon 
the above, rather more than a pound of air to deal with 
at the higher pressure, and this is what actually occurs 
in practice, but is a point which is easily overlooked. 
Now if this air be allowed to expand in a cylinder, it will 
give up more of its heat in order to overcome the resist- 
ance, and in this way it will lose or part with more heat. 
The amount of work done is shown by the indicator card, 
and can be estimated. The mechanical work done by 
the air in this expansion is exactly the same as that 



426 ENGINEERING 

done upon it during its compression, but there is in addi- 
tion the further loss of energy, due to the internal work 
done in the air during the expansion, so that what has 
been done to the air during the entire process has been 
to extract some of its original store of heat, thus reducing 
its temperature ; and the cold air is now ready to restore 
its deficiency at the expense of the surrounding hotter 
bodies. 

It should be borne in mind by the student that all 
bodies contain more or less heat and that heat can neither 
be created nor destroyed because it remains a fixed quan- 
tity throughout the universe. 

Therefore the only method by which the temperature 
of a body or substance can be reduced is by the trans- 
ference of more or less of the heat contained in the body 
to some other body or substance. 

The work demanded of a refrigerating machine is to 
extract heat from a cold body, say from the air in an 
enclosed space, such as a refrigerating chamber, and by 
the expenditure of mechanical energy to sufficiently raise 
the temperature of this heat to admit of its being carried 
away by a suitable external agent, the latter being most 
usually water, which is not only the cheapest one avail- 
able, but also has a greater capacity for heat, weight for 
weight, than any other- known substance, and is taken as 
the standard of comparison, its specific heat being taken 
as unity. 

A refrigerating or ice-making machine may then 
properh^ be defined as a heat-pump for the simple reason 
that its main function is the abstraction of heat from 
one body (the body to be cooled) and continuously and 
automatically transferring that heat to the refrigerating 
or cooling agent. 



REFRIGERATION 427 

'ilie various inventions for refrigerating and ice-mak- 
ing that are now in use, can be conveniently classified for 
the present purpose under the following five principal 
heads, viz. : — 

First, those wherein the more or less rapid dissolution 
or liquefaction of a solid is utilized to abstract heat. 
This is, strictly speaking, more a chemical process. 

Second, those wherein the abstraction of heat is effected 
by the evaporation of a portion of the liquid to be cooled, 
the process being assisted by an air-pump. This is known 
as the vacuum system. 

Third, those wherein the abstraction of heat is effected 
by the evaporation of a separate refrigerating agent of 
a more or less volatile nature, which agent is subse- 
quently restored to its original physical condition by 
mechanical compression and cooling. This is called the 
compression system. 

Fourth, those wherein the abstraction of heat is ef- 
fected by the evaporation of a separate refrigerating 
agent of more or less volatile nature under the direct 
action of heat, which agent again enters in solution with 
a liquid. This is termed the absorption system. 

Fifth, those w^herein air or other gas is first com- 
pressed, then cooled, and afterwards permitted to expand 
whilst doing work, or practically by first applying heat, 
so as to ultimately produce cold. These are usually 
designated as cold-air machines. 

Of the various systems of refrigeration using different 
refrigerating mediums, only two, namely the ammonia 
compression system and the ammonia absorption system 
have comie into anything like general use in this country, 
and these two systems the author proposes to take up and 
discuss in a practical way beginning with the compres- 
sion system. 



428 EISGINEERING 

In this system the process of refrigeration is divided 
into three distinct stages, viz. : — compression, condensa- 
tion, and expansion. 

Anhydrous ammonia is selected as the refrigerating 
medium on account of its low boiUng point ( — 28.6° F.), 
its high latent heat of vaporization, its non-corrosive 
effect on iron and steel, and because the pressures under 
which it is used are such as to render it perfectly safe 
to handle with properly constructed apparatus. 

When nitrogen and hydrogen combine to form ammo- 
nia one volume of nitrogen unites with three volumes of 
hydrogen, hence the chemical formula of ammonia is 
NH3. As the atomic weight of nitrogen is 14 and of 
hydrogen i, the formula also indicates that 14 parts, by 
weight, of nitrogen, combine with 3 parts of hydrogen, 
to create 17 parts of ammonia. 

Gaseous ammonia can be liquefied at a pressure of 128 
lbs, to the square inch, at a temperature of 70° Fahr., and 
at a pressure of 150 lbs. at a temperature of yy"" Fahr., 
the pressure required to produce liquefaction rising very 
rapidly with the temperature. To liquefy by cold it re- 
quires to be reduced to a very low temperature, viz., — 
85.5° Fahr. 

The gaseous ammonia is drawn into the ammonia com- 
pressor, or pump, and is there compressed to a pressure 
varying from 125 to 175 pounds per square inch. 

During this compression, the latent heat of the vapor 
(that is, that quantity of heat which was imparted to it 
to effect its expansion from a liquid to a vapor) is con- 
verted into active or sensible heat. 

The vapor, under this high pressure, is forced into the 
condenser, consisting of a series of pipes over which 
cold water is allowed to flow (atmospheric condenser) 



REFRIGERATION 429 

or through pipe coils submerged in a body of cold water 
(submerged condenser), where the now active and sen- 
sible heat developed during compression is transferred 
to the cooling water, thus withdrawing from the vapor 
that heat which was necessary to keep it in a gaseous 
condition, and re-converting it into a liquid at the tem- 
perature and pressure existing in the condenser. 

The ammonia, so liquefied in the condenser, is then 
allowed to pass in small quantities through a regulating 
or expansion valve into pipe coils placed in the rooms 
to be cooled, or in a bath of brine, w^hen it again expands 
into a vapor, owing to the lower pressure maintained in 
such pipes,, taking up from whatever substance surrounds 
it, an amount of heat exactly equivalent to that which 
zvas given up during condensation. 

The expanded vapor is then drawn back into the com- 
pressor, again compressed, condensed, and expanded, the 
cycle of operation being repeated indefinitely with the 
same ammonia, which is used continuously and which 
never comes in contact with the substance to be refrig- 
erated. 

There are two systems of refrigeration by compres- 
sion, viz, : the ''wet'' system and the ''dry" system. 

As the Linde ice-machine manufactured by the Fred 
W. Wolf Co. of Chicago is a good example of the work- 
ings of the "wet" or humid system, a short description 
of the construction and operation of the machine will be 
given. (Fig. i6o.) 

The theory of the action of the Linde machine is as 
follows : 

So long as ammonia vapor is in a humid or saturated 
condition (that is, while still in contact with any of its 
originating liquid), temperature and pressure are func- 



430 



ENGINEERING 






H 




^ 




1— 1 




ffi 


d 

CO 






^ 


H 




oi 


H 


^ 


U 


2 


1— 1 






E 


H 




Q 




^ 



si#^ 



REFRIGERATION 431 

tions of one another, and to a given temperature belongs 
a certain pressure. 

On the contrary, when ammonia (now properly called 
a gas) is not in contact with any of its mother liquid, its 
temperature may be very much higher than that cor- 
responding to its pressure. 

For example, the pressure of the steam in a boiler 
depends entirely upon its temperature, which is always 
equal to that of the remaining water. It is therefore evi- 
dent that in the case of steam, while in contact with the 
originating water, temperature and pressure are interde- 
pendent. 

Separate the steam from the water, and apply heat 
(superheat it), and it may have the same pressure at 
widely different temperatures. 

When a gas or vapor is compressed, the heat equiva- 
lent of the mechanical w^ork of compression tends to raise 
its temperature, and consequently its pressure, more rap- 
idly than would be the case if it would be maintained 
at constant temperature. 

In the compression of a dry gas, unless heat is with- 
drawn by means of a water-jacket, or other cooling de- 
vice, the adiabatic curve will be traced on the indicator 
diagram. This is the curve which represents the com- 
pression or expansion of a gas without loss or gain of 
heat. 

In the Linde machine the cooling of the vapor in the 
compression cylinder is effected by the introduction into 
the latter of a small quantity of liquid ammonia with 
the gas or vapor at the commencement of each stroke 
whereby it is cooled down to a refrigerating temperature. 
The ammonia is carried back to the compressor in a 
saturated condition and the heat of compression is taken 



432 



ENGINEERING 



care of in the unexpanded ammonia which in the form of 
fog or vapor, entered the compressor on the suction 
stroke. 

The diagrams Figs. i6i and 162 illustrate the com- 
parative efficiency of this method of cooling the compres- 
sion cylinder, termed the *'wet" system, and the other 



\s o*r H«.v^rAA^\. 



^QVO 1 40.^ «k Jt%^ IC» 



10 

5 

o 



Spring 60 

M. E. P. 59 Lbs. 
....-Area 0.05°' 
..^- Area 0.69^' 







Dry Oas, 
FIGURE 161. 



method wherein a water-jacket system is employed termed 
the '*dry'' gas system. 

The initial volume and pressure and the terminal pres- 
sure are the same in each case. In the compression of 
the dry gas, the compression curve necessarily follows 
for a considerable distance the adiabatic line. 



REFRIGERATION^ 



433 



This for the reason that the gas coming into the cylin- 
der from the expansion coils is at a temperature of — 5^ 
F. and no heat can be transmitted from it to the cooling 
water in the water-jacket until the temperature of the 
gas has been raised above that of the water, which is 
probably. 60° to 70° F. 



««O«rH1Ll^M>0^W • 



Spring 60 

M. E. P. 53 Lbs. 

Area 0.4°' 




Saturated Vapor. 
FIGURE 162, 



The compression curve then leaves the adiabatic and 
during the last part of the stroke, before the discharge 
valve opens, approaches the isothermal line. 

In the compression of saturated vapor, the unexpanded 
ammonia begins immediately to absorb the heat of com- 



434 REFRIGERATIOJS 

presslon and the compression curve at once leaves the 
adiabatic and approaches the isothermal Hne, making a 
diagram that is much smaller in area and which therefore 
represents work requiring less power. 

The efficiency ratio of any cylinder cooling device is 
found by dividing the area between the actual compres- 
sion curve and the adiabatic curve, by the total area be- 
tween the adiabatic and isothermal curves. 

Assuming that the diagrams shown are from eighteen 
by thirty inch double-acting compressors, running at 
fifty revolutions per minute, the effective horse-power 
required for the compression of the saturated vapor would 
be I02.I horse-power, as against 113.7 horse-power for 
the dry-gas machine, a gain of 10.2% in favor of the 
humid system of operation. 

Fig. 163 shows a sectional view of the compressor 
cylinder, piston, and valves. It will be observed that the 
piston and heads are spherical and of the same radius. 
The valve discs conform absolutely to this radius, and 
when the valves are seated these discs are exactly flush 
with the heads. 

The clearance between the piston and the cylinder head 
is very small, being only 1/32 in., therefore the clearance 
losses are very small, being less than two per cent, of 
the total cylinder volume. The cylinders are made of 
clear, hard iron, tested to 1,000 lbs. hydrostatic pressure. 
The finishing cut through the cylinder is made after it 
is placed in the frame, the final cut on crosshead guides 
being taken at the same time, and on the same boring 
bar, thus insuring their correct alignment. Proper open- 
ings are provided for the application of the indicator. 

The lubrication of the piston is accomplished in large 
measure by the moisture in the ammonia itself. Oil is 



REFRIGERATION 



435 



used to seal the stuffing box against the leakage of am- 
monia. Very little of this oil is carried into the cylinder 
on the piston rod. 

The piston is ground on the tapered shoulder of the 
piston rod, and is secured by lock nuts, as shown in Fig. 
163. The follower head is then screwed on and held 




FIGURE 163. 
Sectional view of tlie Linde compressor cylinder and valves. 



'firmly in place by the flush nut, which in turn is pre- 
vented from backing off by a screw set into the face of 
the follower and riveted over. Those who have experi- 
enced the annoying effect of pistons working loose on the 
rod will appreciate the advantages of this method, per- 
mitting, as it does, the ready removal of the piston when 
necessary, while at the same time absolutely precluding 



436 ENGINEERING 

the possibility of its accidentally becoming loose. Many 
serious accidents have resulted from inattention to this 
detail. The piston is packed with removable bull rings 
and cast-iron packing rings. 

The valves are of large area, the discharge valve being 
placed at the lowest point of the cylinder, insuring the 
perfect draining of any liquid present at the end of the 
compression period. The importance of this feature can- 
not be overestimated ; the many records of compressors 
wrecked by the piston coming in contact with incompres- 
sible liquid being familiar to all users of this class of 
machinery. The stems and discs are of the finest forged 
steel, set in cast-steel housings. The valve lift is gov- 
erned by positive stops and controlled by springs. The 
suction valve is provided with a safety stop to prevent 
its falling into the cylinder. 

The Linde stuffing box is shown in section, in Fig. 164 
— to which reference is now made. The numbers 2, 4, 
5, 9, 10, 12 and 14 indicate composition packing rings. 
These should never be used solid but should be cut as 
shown in sketch ''A." Numbers 3, 6, 8^, and 11 repre- 
sent metal rings, made from pure tin. They are in- 
tended to keep the rubber rings in proper condition. 
These rings should always be one-sixteenth of an inch 
larger than the rod and should never be cut in two, as 
otherwise they are apt to score the rod. If necessary 
to put in new metal rings, disconnect the piston rod 
from the crosshead and slip the rings over the end of 
the rod. Under no circumstances pack the compressor 
zvithout the metal rings. 

Number 7 designates the lantern which forms an oil 
storage in the middle of tlie stuffing box. The oil supply 
is taken in at the point marked "a" through a pipe con- 



REFRIGERATION 



437 




FIGURE 164. 

Sectional view of Linde Stuffing Box. 



438 ENGINEERING 

nection from the oil trap. This passage being always 
open, the oil is forced into the stuffing-box by the high 
pressure gas in the oil trap, keeping this stuffing-box and 
lantern always full and instantly replacing what little 
oil is carried into the cylinder on the rod. Number 13 
is the stuffing-box gland which is supplied with oil 
through the inlet ''b'' from a small oil pump operated 
from the main shaft. This oil overflows at "c" and i:3 led 
back to the oil pan to be recirculated. 

Number 15 is the oil gland which should be kept just 
tight enough to keep the oil in the stuffing-box gland. 
The points of contact with the rod are numbers, i, 13, 
and 15, and they must fit the rod properly. If it be- 
comes scored and is turned down, these parts must be 
rebabbitted. 

When repacking be sure to place the different parts 
of the packing in strict accordance with the above in- 
structions and with the cut shown, insuring the best re- 
sults. Great care should be used not to tighten the 
stuffing gland 13 more than is necessary to prevent the 
amm_onia from leaking. 

The Linde compressor is of the horizontal double 
acting type, and consequently the lines of strain are 
brought close to, and parallel with the foundations. The 
machine is so constructed, as to be easily attached to any 
steam engine, either by being direct connected, or by 
belting from a counter shaft. In small plants, electric 
motors are often used for operating these machines. Fig, 
165 shows an installation of this kind. 

There are two distinct methods of utilizing refriger- 
ation ; viz. ; the Brine System and the Direct Expansion 
System, In the former the coils of pipe in which the 
ammonia is expanded are placed in a tank containing a 



REFRIGERATION 



439 



solution of salt or calcium chloride of such density as 
to insure a low freezing point. This body of brine, after 
being reduced to a low temperature by the transfer of 
its heat to the expanding ammonia, is pumped through 
coils of pipe in the rooms to be cooled, taking up from 
the atmosphere of such rooms a part of its heat. It is 
then returned to the brine tank, recooled and again cir- 
culated through the rooms. 



1 ^^^^^^^B[^ ^r il^^fe^Y^^ 


?'^^P ^^M#-*#?B ^ffl 


H 






^^^^^^^^^^^^^^K| 1 


^^^^M^^^-. -i^^^^^j 






r??v;*:^^^^^^;v| 


^^^^■t. 








■-£ ■^^-i.^ i. »" 


- * ' 0^ '^ i' 


2 



FIGURE 165. 

12-ton Linde ice machine — motor operated. 



In the Direct Expansion System the expansion pipes 
are placed in the rooms to be cooled, the heat necessary 
for the expansion of the ammonia being drawn directly 
from the atmosphere surrounding the pipes. 

Of the two systems, the direct expansion system is 
probably the most efficient as may be seen by the follow- 
ing summary of its advantages over the brine system : 

1st. All intermediate agencies are dispensed with, ^he 
refrigeration being produced at the place where it is 



440 ENGINEERING 

utilized. Every transfer of energy means loss. The 
brine tank, even if insulated, furnishes immense sur- 
face for loss by radiation. 

2d. The whole plant is much simpler, considerable 
auxiliary apparatus, such as pumps, etc., is unnecessary, 
the requirement of power is therefore reduced and re- 
pairs are correspondingly lessened. 

3d. The expansion surface is enlarged and better dis- 
tributed, making possible the using of the entire capacity 
of the compressor to the best advantage. 

4th. The ammonia is expanded at a much higher 
temperature and pressure, and is therefore drawn back 
to the compressor at higher density, resulting in the 
m.achine circulating a much greater weight of ammonia 
per minute. Each pound of ammonia has just so much 
potential refrigerating energy and the capacity of a com- 
pressor is therefore dependent solely upon the weight 
of ammonia pumped in a given time. For example, if it 
is desired to maintain a temperature of 32° F. in a cer- 
tain room, it will require a compressor displacement of 
22 per cent, more with the Brine System than with 
Direct Expansion. 

5th. The Brine System is much more expensive to 
install, owing to the far greater quantity of pipe required, 
the additional pumps, tanks, etc. 

One of the advantages claimed for the Brine System is 
the ability to store refrigerating energy in the brine tank, 
which may be drawn upon during the night, thus ren- 
dering the continued operation of the compressor unnec- 
essary. It has been claimed that by doing this the fuel 
consumption is reduced ; but this is not good logic, since 
just so much work must be done to produce a given 
quantity of refrigeration and it makes no difference 



441 

twenty- 

If the 

»r must 



during 
This 

pubHc 
, from 
ral ice, 
plants, 

found 
uHarly 
ler in- 

em or 

ice by 
•rocess 
steam, 
ensed, 
.11 the 
it will 

'ange- 
water. 
aia is 
g ex- 
tank. 

drive 
;es to 
jh an 
latter 



AFlRANeeMENT OF AN ICE PLANT 



«. BOrLEH. 
2.FEEO PUMR 
i STEAM ENGINE 
A COMPRESSOR 
_ FOR A 
CONDENSER. 

ReCEIVER. 
SEPARATOR 



REBOIUER 

COOLING COIL 

nuTERS. 

COUD WATER RESERVOIR 

'^■- ■ INS h|OSE 




Figure 166 



REFRIGERATION 441 

whether this work is distributed throughout the twenty- 
four hours or is crowded into a shorter period. If the 
work is to be done in a short time the compressor must 
be correspondingly larger. 

The development of the ice-making industry during 
the past ten years has been astonishingly rapid. This 
may be attributed to the fact that the ice-using public 
has come to a realization of the vast superiority, from 
a hygienic standpoint, of manufactured over natural ice, 
and to the further fact that owners of electric light plants, 
mills, water-works and other power plants have found 
that the ice-making business is one that is peculiarly 
adapted to being operated in combination with other in- 
dustries requiring the use of power. 

Ice is made artificially by either the Can System or 
Plate System. 

In order to obtain absolutely pure and crystal ice by 
this system, a complete distilling and filtering process 
must be employed. Water, when evaporated into steam, 
parts with all of its impurities ; the steam is condensed, 
the water of condensation being entirely pure. All the 
air must then be expelled from it, as otherwise it will 
freeze into opaque or so-called *^snow'' ice. 

The inserted illustration. Fig. i66, shows an arrange- 
ment for the production of can ice from distilled water. 
The compression and condensation of the ammonia is 
carried on as already described, the ammonia being ex- 
panded in expansion coils placed in the freezing tank. 
(No. i8.) 

The steam generated in the boiler is first used to drive 
the steam engine. The exhaust steam then passes to 
the steam condenser (No. lo), first passing through an 
oir extractor (No. 9), where any lubricrating matter 



442 ENGINEERING 

which has been carried along from the cylinder is re- 
moved. The steam condenser is designed on the same 
principle as the ammonia condenser, being a series of 
pipes over which cooling water is allowed to flow. The 
exhaust steam is not usually sufficient to make the full 
capacity of ice, and sufficient live steam is therefore sup- 
plied to the steam condenser to make up the deficiency. 
The water resulting from the condensing of the steam 
passes to the skimmer (No. ii), where any oil that may 
pass the oil extractor is removed. 

From the skimmer the water goes to the re-boiler (No. 
12), at the bottom of which is placed a small steam coil 
by means of which the water is kept boiling and the 
air contained in it expelled. It then passes to the flat 
cooler (No. 13), an apparatus similar to a condenser, 
where its temperature is reduced to that of the cooling 
water available. Thence it is led to the filters (No. 14), 
which are furnished in duplicate so that one may be 
shut off and cleaned without interfering with the opera- 
tion of the plant. In special cases, where the nature of 
the water requires it, sponge, silicate, or bone charcoal 
filters are used. From the filters the water passes to 
the cold-water storage tank (No. 15), which contains 
an ammonia expansion coil. By the use of the coil the 
distilled water is reduced to the freezing temperature 
before going into the freezing cans. 

By means of a can filler (No. 17), so arranged that 
the water is automatically shut off when the can is filled 
to the proper depth, the galvanized iron freezing c^s 
are filled with distilled water from the cold-water tank. 
The freezing tank (No. 18) is usually made of iron 
or steel and thoroughly insulated at the bottom and sides. 
It is provided with suitable hardwood frame and covers 



REFRIGERATION 



443 



and has an efficient agitating device for keeping the 
brine in motion. The brine acts as a medium for the 
transfer of the heat from the distilled water within the 
cans to the expanding ammonia in the expansion coils, 
which are placed longitudinally of the tank and between 
which the cans are inserted. 

The ice when frozen is hoisted out of the tank by 
means of the hoisting apparatus (No. 19). The ice is 
loosened from the cans by the use of warm water from 
the condenser, either by employing a sprinkling ap- 
paratus (No. 20) or by dipping the can bodily into a 
tank. 

TABLE 20. 
Tabi,e Giving Number of Cubic Fekt of Gas that must 
BK Pumped per Minute at Different Condenser and 
Suction Pressures, to Produce One Ton of Refrig- 
eration IN Twenty-four Hours. 






tt^a 




Temperature of the Gas i 


n Degrees F. 




.5S- 

CO <V 
<V C p. 


65^ 


70^ 


75^ 


80^ 


85^ 


90^ 95^ 100° 105^ 


43 b£ 
















o§3 


Corresponding Condenser Pressure ( 


gauge), lbs. per Sq. In. 


ft 


QQ 


103 


115 


127 


189 


158 


168 184 200 218 




G.pres 




















-27 


1 


7.22 


7.3 


7.87 


7.46 


7.54 


7.62 


7.70 


7.79 


7.88 


-20 


4 


5.84 


5.9 


5.96 


6.08 


6.09 


6.16 


6.23 


6.30 


6.43 


-15 


6 


5.35 


5.4 


5.46 


5.52 


5.58 


5.64 


5.70 


5.77 


5.83 


-10 


9 


4.66 


4.73 


4.76 


4.81 


4.86 


4.91 


4.97 


5.05 


5.08 


- 5 


13 


4.09 


4.12 


4.17 


4.21 


4.25 


4.80 


4.85 


4.40 


4.44 





16 


3.59 


3.63 


8.66 


8.70 


3.74 


3.78 


3.83 


3.87 


3.91 


5 


20 


3.20 


3.24 


3.27 


3.80 


8.84 


8.88 


3.41 


3.45 


3.49 


10 


24 


2.87 


2.9 


2.93 


2.96 


2.99 


3.02 


3.06 


3.09 


3.12 


15 


28 


2.59 


2.61 


2.65 


2.68 


2.71 


2.73 


2.76 


2.80 


2.82- 


20 


83 


2.31 


2.34 


2.36 


2.38 


2.41 


2.44 


2.46 


2.49 


2.51 


25 


39 


2.06 


2.08 


2.10 


2.12 


2.15 


2.17 


2.20 


2.22 


2.24 


30 


45 


1.85 


1.87 


1.89 


1.91 


1.93 


1.95 


1.97 


2.00 


2.01 


35 


51 


1.70 


1.72 


1.74 


1.76 


1.77 


1.79 


1.81 


1.83 


1.85 



444 



ENGINEERING 



In the De La Vergne refrigerating machine the cool- 
ing of the heated gas is efifected by passing it through 
pipes surrounded by running water. The characteristic 
feature of this machine consists in the patented system 
for preventing the occurrence of any leakage of gas 
taking place past the stuffing box, piston, and valves, and 
of extracting the heat from the gas during compression, 
by the simple device of injecting into the compressor, at 
each stroke, a certain quantity of oil or other suitable 
lubricating fluid. By means of this sealing, lubricating 
and cooling oil, not only are the stuffing box, piston, and 




FIGURE 167. 

Double-acting type of De La Vergne ammonia compressor. 



valves efifectually sealed, and the heat developed during 
compression taken up, but all clearances are entirely 
filled up. This latter is a matter of great importance, 
as it ensures a complete discharge of the gas from the 
pump cylinder, and obviates the above-mentioned loss 
of power and efficiency. 

This method of sealing the stuffing box and piston 
prevents leakage and consequent introduction of air into 
the pump, or wasting of the refrigerating gas at each 
alternate stroke of the piston without necessitating the 



REFRIGERATION 445 

packing of piston so tightly as to cause excessive fricion. 
Fig. 167 shows a sectional view of a double acting De 
La Vergne compressor jfitted with Louis Block's arrange- 
ment of valves, the main object of which is to secure 
the discharge of the oil at the lower end of the cylinder 
taking place immediately after all the gas is gone and 
not before, as in the latter case re-expansion will take 
place, resulting in loss of efficiency of the pump. To 
effect this, two valves are provided in the lower end of 
tlie compressor cylinder, one above the other. 

Either or both of these valves may open on the down 
stroke of the piston, until the latter covers the upper one, 
when only the lower one is left open to the condenser. 
During the remainder of the stroke of the piston, after 
the low^er valve is also closed, the other or upper one 
opens communication with an annular chamber formed 
in the said piston. In the bottom of this annular cham- 
ber are provided, moreover, valves which open as soon 
as all the other outlets from the underside of the piston 
are closed, to ensure which they are loaded with springs, 
so arranged as to require somewhat more pressure to 
open them than the discharge valves on the side of the 
cylinder. The gas, and afterwards the oil, then all pass 
out through the piston, no trace of the former being 
present at the completion of the down .stroke. In this 
manner the oil system of sealing can be advantageously 
retained, and the pump wdll work as well at the lower 
side as the upper. 

Fig. 168 shows a complete installation of a refriger- 
ating plant on the De La Vergne system, the vertical 
compressor being driven by a horizontal engine. The 
circulation of the ammonia„ and the sealing oil is as fol- 
lows : A is the compressor cylinder, double acting, and 



446 



ENGINEERING 






C3 


b/) 


w 


a 


fl 


tf 


•42 


^ 


0, 




c^ 




<L> 






bfl 


K 


0) 


;-• 












a» 




ft 


;-• 



REFRIGERATION 447 

similar in construction to that shown in section in Fig. 
167. R is the steam engine cylinder. B is the pipe 
through which the gas is drawn from the evaporating 
coils into the compressor A. The gas is then discharged 
by the action of the compressor through the pipe C, into 
the pressure tank D, where the sealing oil or liquid falls 
to the bottom. Suitable cast-iron baffle plates are fitted 
in the upper portion of the pressure tank, which serve 
to retain the oil, and insure its deposition. From the 
pressure tank d the gas which still retains the heat due 
to compression, passes through pipe e into the bottom 
or lower pipe of the condenser f^ wherein, by the cooling 
action of cold water running over the pipes, the heated 
gas is first cooled and then liquefied. The ammonia, in 
this liquid condition, is then led by the small liquid pipes 
G, through the liquid header h, into the storage tank i, 
from whence it flows through the pipe j into the lower 
part of the separating tank k, which latter must be con- 
stantW maintained at the very least three-quarters full. 
L is a pipe of small bore, through which the liquid am- 
monia is forced, by reason of the pressure to which it 
is now subjected, to the expansion cock or valve, through 
which it is injected into the evaporating or expansion 
coil N which is situated in the room or chamber to be 
refrigerated or cooled. 

The ammonia gas resulting from the expansion and 
evaporation of the liquid ammonia in the evaporating or 
expansion coil n, having absorbed or taken up the heat 
from the surrounding atmosphere, passes away through 
the pipes o and b, back again into the compressor cylin- 
der, and the cycle of operations of compressing, etc., are 
again performed as above. 

Secondly. Following the course of the oil employed 



448 ENGINEERING 

for sealing, lubricating, and cooling purposes, which, as 
previously mentioned, is heated with the gas during com- 
pression, and is passed into the tank d, to the bottom of 
which it falls. From the bottom of the tank d, the heated 
oil is conducted through a pipe a to the lowermost pipe 
of the oil-cooler b, which is practically similar in con- 
struction, but on a smaller scale, to the ammonia con- 
denser, and is likewise cooled by sprayed or atomized 
cold water. After being sufficiently reduced in tempera- 
ture in the oil-cooler h, the oil flows through the pipe c, 
strainer d, and pipe e, into the oil pump /, which latter 
IS so constructed that it delivers the cooled oil into the 
compressor, distributing it to either side of the piston or 
plunger during its compression stroke, that is to say, in 
such a manner that no oil is furnished during the suction 
stroke of the piston, but only during the time of com- 
pressing, thereby cooling the gas during its period of 
heating. The heated oil, after leaving the compressor, 
then again returns, together with the hot compressed gas, 
to the pressure tank d, and follows the same round 
through the oil-cooler h, strainer d, and oil pump /, back 
to the compression cylinder. It will be obvious that the 
oil, as well as the ammonia, is used over and over again, 
no loss or waste of either taking place except that which 
may occur through leakage. 

Any small quantities of oil, how^ever, that may be car- 
ried over with the current of the gas from the pressure 
tank D into the condenser f, pass along with the liquid 
ammonia into the separating tank k, where, by reason 
of its greater weight, this oil falls to, and collects at the 
bottom of the tank. As soon as a sufficient quantity of 
oil has become thus deposited, it is drawn off, and passed 
through the oil cooler back to the oil pump. The oil 



REFRIGERATION 



449 



reservoir or tank is also connected to the oil pump f. 
When the apparatus is employed for the manufacture of 
ice, the evaporating coils n are placed in a tank contain- 
ing brine, sufficient space being left between them to 
allow of the insertion of cans or moulds containing the 
water to be frozen. As before stated the exhaust steam 
of the engine driving the compressor is condensed and 
purified, and supplies the water to be made into ice. 




FIGURE 169. 
Diagram from De Lavergne Compressor. 

The various parts are clearly indicated in Fig. i68 — 
and the routes taken by the ammonia, the sealing oil, the 
lubricating and cooling oil, and the steam are shown by 
the arrows. 

Fig. 170 is a sectional view of the Triumph Ice Ma- 
chine Company, Cincinnati, O., horizontal pattern dou- 
ble-acting ammonia compressor. It will be seen from the 
illustration that the compressor is provided with five 
valves, viz., three suction valves and two discharge 



450 



ENGINEERING 



valves, the third, or auxiliary suction valve, being much 
lighter than the main valves, and perfectly balanced, and 
it being claimed by the makers tending greatly to increase 
the economy of the machine. 

Obviously the main suction valves must necessarily be 
of sufficient dimensions to admit the charge quickly at 
the commencement of each stroke, and the springs con- 




FIGURE 170. 
Double-action horizontal type of Triumph ammonia compressor. 



trolling them must consequently have an appreciable ten- 
sion. It will be readily seen that owing to this fact the 
pressure of the gas in the cylinder, during admission, 
must be less than it is in the suction pipe by an amount 
equal to the tension of these springs. By the use of the 
above mentioned third, or auxiliary suction valve, which 
is comparatively light, and is consequently operated with 
a very light spring, the pressures in the compressor pump 



REFRIGERATION 451 

are equalised, and a fuller charge is obtained at each 
stroke, thereby increasing the efficiency of the machine. 

The valves comprise each a guard screwed on to the 
stem, fitted inside a cage, and so ribbed as to reduce the 
port area, the bottom of the stem being enlarged for that 
reason. Stems extending from both the suction and dis- 
charge valves to the exterior, and passing through stuff- 
ing boxes, admit of their being adjusted from the outside, 
and any desired degree of tension being put upon the 
springs. The object of this arrangement is to adjust the 
machine for working at different pressures, and the rela- 
tive temperatures thereof. 

There are three packing compartments in the piston- 
rod stuffing box, and it is fitted with a suitable relief 
valve communicating with the suction. The heads are 
formed concave, and of a radius which enables a larger 
valve area to be secured. The principal shut-off valves 
are of such a form of construction as to admit of their 
being packed whilst the machine is working, and a fea- 
ture in the design of this machine which is of by no 
means inconsiderable advantage, is that every portion of 
the compressor is easily accessible. 

Besides ammonia, there are various other refrigerating 
agents employed in the compression system, among 
which may be mentioned Ether, Methyl-chloride, sul- 
phurous acid, and carbonic acid, but space will not per- 
mit a further discussion of the compression system, and 
the absorption process will now be taken up. 

The principle involved in the operation of apparatus 
for the abstraction of heat by the evaporation of a sepa- 
rate refrigerating agent of a volatile nature under the 
direct action of heat, and without the use of power, 
which agent again enters into solution with a liquid, is, 



452 ENGINEERING 

more a chemical or physical action than a mechanical 
one. It is founded upon the fact of the great capacity 
possessed by water for absorbing a number of vapors 
having low boiling points, and of their being readily sep- 
arable therefrom again, by heating the combined liquid; 
hence it is commonly known as the absorption process. 

The absorption process was invented by Ferdinand 
Carre about the year 1850. This system involves the 
continuous distillation of amxmoniacal liquor, and re- 
quires the use of three distinct sets of appliances, viz: — 

First, for distilling, condensing, and liquefying the 
ammonia. Second, for producing cold, by means of a 
refrigerator, and absorber, a condenser, a concentrator, 
and a rectifier. Third, pumps for forcing the liquor from 
the condenser into the generator for redistillation. The 
three operations are each distinct from the other, but 
when the apparatus is in actual work they must be con- 
tinuous, and are dependent upon one another, forming 
separate stages of a closed cycle. 

An advantage of the absorption process is that the bulk 
of the heat required for performing the work is applied 
direct without being transformed into mechanical power. 
The first machines, however, constructed upon this prin- 
ciple were very imperfect in operation, by reason of the 
impossibility of securing an anhydrous product of dis- 
tillation, and as the ammonia distilled over contained as 
much as 25 per cent of water, a very large expenditure 
of heat was required for evaporation, and the working 
of the apparatus, moreover, was rendered intermittent. 
This was owing to the distillation, which is the most im- 
portant operation, and has of necessity to be executed 
in a rapid manner, being, in the first machines, very im- 
perfectly effected, and the liquor resulting therefrom 



REFRIGERATION 453 

being naturally much diluted with water. Another seri- 
ous result of the above defect was the accumulation of 
weak liquor in the refrigerator, and the consequent 
necessity for constant additions of ammonia. 

Fig. 171 illustrates an ammonia absorption, refrigerat- 
ing device, one of a leading American type, and will give 
a clear idea of the operation in general of the system. 

A constant pressure of about 150 lbs. per square inch 
is maintained in the generator, and to prevent this pres- 
sure from being exceeded, a safety valve is provided 
on the dome of the generator. The gas that escapes 
through this safety valve is led through a suitable pipe 
to a smiall water tank, where it is absorbed. The opera- 
tion is as follows : 

The aqua ammonia is first introduced into the genera- 
tor, the gas or vapor expelled therefrom by heat into 
the condenser; and so that the process may be carried 
out continuously and not be arrested by the exhaustion 
of the solution, the exhausted or impoverished liquor 
is slowly drawn ofif at the bottom of the generator, an 
equal volume of fresh strong solution being constantly 
inserted at the top thereof. The united effects of the 
cooling and pressure produce liquefaction of the ammo- 
niacal gas or vapor in the condenser, and the liquid am- 
monia passes to the refrigerator. It will be seen that 
the ammoniacal gas or vapor from the tubes of the re- 
frigerator is re-absorbed, and a rich solution is formed 
to feed the generator, the absorbing water used being 
that withdrawn exhausted from the latter. Thus the 
generator and the condenser will keep up a continuous 
supply of the liquid, and the refrigerator will continue 
to freeze successive charges of water in the ice-cans or 
cases, provided, however, that the requisite heat to va- 



454 



ENGINEERING 




REFRIGERATION 455 

porise or gasify the ammonia is supplied to the generator. 
If, therefore, the entire apparatus be perfectly fluid- 
tight, as it is theoretically supposed to be, no escape could 
take place by leakage or otherwise, and the same ma- 
terials would go on indefinitely producing the same uni- 
form effect. 

In starting a machine constructed on the absorption 
principle it must be first blown through to expel all the 
air. In Carre's apparatus the air escaping from the ab- 
sorber is conducted by a suitable pipe into what is known 
as a purger, where it is passed below the surface of 
water to absorb or retain any ammonia that would other- 
wise escape with the air. 

A large amount of water is required for cooling pur- 
poses in the condenser or liquefier, and absorber, and a 
considerable consumption of fuel is also necessary to heat 
the generator, when this is performed directly by means 
of a furnace. When, however, this is effected by steam- 
heated pipes, or, by coils of pipe heated by the ex- 
haust steam from an engine, or even by direct or live 
steam from a boiler, there is a considerable saving on 
this head. vSteam or other motive power is likewise re- 
quired for driving the force pump. 

The operation of Recce's improved apparatus is briefly 
as follows: — 

The charge of liquid ammonia (the ordinary commer- 
cial quality of a density of 26° Beaume) is vaporised by 
the application of heat, and the mixed vapor of water 
and ammonia passed to the vessels called the analyser 
and the rectifier, wherein the bulk of the water is con- 
densed at a comparatively elevated temperature, and is 
returned to the generator. The ammoniacal vapor or 
gas is then passed to the condenser, where it is treated 



456 ENGINEERING 

in a substantially similar manner to that in Carre's ap- 
paratus, that is to say, it is caused to liquefy under the 
combined action of the condensation effected by the cool- 
ing water circulating around the condenser tubes, and of 
the pressure maintained in the generator. The liquid 
ammonia (in this case practically anhydrous) is then 
used in the refrigerator, and the vapor therefrom, 
whilst still under considerable tension, is admitted from 
the refrigerator to a cylinder fitted with a slide valve, 
and entry and exhaust ports, practically similar to those 
of a high pressure steam-engine, and is thus utilized to 
drive the force pump for returning the strong solution 
to the generator, after which it is passed into the ab- 
sorber, where it meets, and is taken up by, the weak 
liquor from the generator, and the strong liquor so 
formed is forced back into the generator by means of a 
force pump. 

Figure 172 shows the general form of the Consolidated 
ice-making and refrigerating machine. It is a compres- 
sion type of machine, having two single-acting, vertical 
compressors and either a horizontal or a vertical engine, 
which is connected to a center crank, on either side of 
which are large journal bearings. Power thus trans- 
mitted to the shaft is regulated by two flywheels which 
are of sufficient weight to carry the engine sm.oothly 
over the point of maximum compression and to deliver 
the power to the compressor. 

It is an adavantage to have the crank in the center 
of the shaft and to place a flywheel between the engine 
crank and each pump crank, because this construction 
gives uniformity and steadiness of motion and dimin- 
ishes torsional strain, vibration and friction of the crank 
shaft. It also permits the use of a long-stroke Cor- 



REFRIGERATION 



457 



liss engine, since the stroke of the engine is not lim- 
ited to the stroke of the ammonia pump, as is the case 
where the compressor and engine are connected to the 
same crank pin. In this way, the builders claim to effect 
a saving of from lo to 15 per cent in the steam con- 
sumption. 




FIGUKE 17 



VERTICAL CONSOLIDATED REFRIGERATING MACHINE. 



Heavy pump columns terminate at the bottom in broad 
flanges bolted to a substantial foundation plate, cast in 
©ne piece and provided with four journal bearings for 



458 ENGINEERING 

the crank shaft. Convenient stairways and galleries are 
provided to furnish access to the upper part of the ma- 
chine. As seen in Fig. 173 the compressor or ammonia 
pump is single-acting, compressing only on the up-stroke, 
and the gas has free entrance to and exit from the 
cylinder below the piston, thus keeping the pump cylinder 
and piston cool. 

An oil chamber, which effectually seals the stuffing- 
box around the pump piston rod, is formed in the lower 
part of the pump. As the pressure on the stuffingbox 
end of the pump is only the direct evaporator pressure, 
there is no chance for the escape of ammonia. Equal- 
ization of the temperature and cooling of the com- 
pressor is effected by encasing it in a copper water 
jacket. 

In the construction of the piston, no bolts or nuts are 
used, and there are, therefore, no cavities or chambers 
into which the gas can be comprest. Since the piston 
travels flush with the pump head, all of the gas is ex- 
pelled at each stroke. The pistons are fitted with spring 
rings that are first turned elliptical and afterward re- 
turned on a mandrel until they fit the cylinder exactly. 

As shown in Fig. 173 the stuffingboxes are operated 
by a worm-gear device so that, while the machine is 
running, a turn of the handwheel accurately adjusts the 
stuffingbox gland and thus makes unnecessary the dif- 
ferent and frequently dangerous use of a wrench or 
spanner and also avoids the possibility of cutting the 
piston rod by uneven adjustment of the gland. 

Connections for the suction and discharge pipes are 
made outside of the pump head so that, when it is 
desired to remove the head, neither of these connections 
need be disturbed. Discharge and suction valves, com- 



REFRIGERATION 



459 




FIGUEE 173. CROSS-SECTION OF THE SIMPLE-ACTING AMMONIA 
COMPRESSOR. 



460 



ENGINEERING 



pressor heads, piston and piston rods, all are easily re- 
moved without breaking any ammonia connections. 

Figure 173 shows the suction and discharge valves 
which are located in the pump head. The suction valve, 
Fig. 174, is balanced, thus allowing the pump to fill with 
expanded gas from the evaporator with no loss of press- 




FIGURE 174. SUCTION VALVE SHOWING SAFETY DEVICE. 



ure. As shown in Fig. 174, the valves are provided with 
a safety device which renders it impossible for them to 
get into the cylinder. Cushioning of the discharge valves 
ensures noiseless action and, since both suction and dis- 
charge valves are set in steel cages and held in position 



REFRIGERATION 461 

in the pump head by means of yokes and set screws, it 
is but a moment's work to remove a valve and put a du- 
plicate in place. 

As seen in Fig. 172 the machine is driven by a Feather- 
stone Corliss engine resting on substantial base plates 
which are extended on one side for the dashpots. The 
valve motion is of the improved Corliss type, having the 
liberating catches made of hardened steel of such form 
that eight wearing surfaces are available, by change of 
position, each new position restoring the valve motion to 
its original setting. 



HORIZONTAL TYPE. 

In this form, the Featherstone machine is built with 
a horizontal engine and a horizontal, double-acting com- 
pressor, and has a straight crank shaft with the flywheel 
placed in the middle between the two main bearings as 
shown in Fig. 175. These machines are mounted on the 
heavy-duty Tangye frame which is almost universally 
used by builders of double-acting compressors. Provision 
is made for cooling the compressor cylinder by means 
of a water jacket so that it may be operated as a dry 
or humid gas machine. As shown in Fig. 175, the ma- 
chine is driven by a Featherstone-Corliss engine, having 
a heavy frame similar to that of the compressor, but 
any type of engine may be used and, if necessary, the 
compressor can be driven by belt. 

Figure 176 shows the manner in which the compressor 
cylinders are pressed into the frame so as to form a water 
jacket. The valves are placed in the compressor head 
in a way that will permit of their easy removal and. 



462 



ENGINEERING 




^m 



REFRIGERATION 



463 




464 ENGINEERING 

since the discharge valves are located at the lowest part 
of the cylinder, perfect draining at the end of the com- 
pression period is assured. This makes it impossible for 
the machine to be wrecked by the piston coming in con- 
tact with an incompressible liquid at the end of the 
stroke. The clearance is less than 1-32 inch, thus giv- 
ing good efficiency by permitting the piston to discharge 
all of the gas at each stroke, so that on commencing a 
new stroke, gas is immediately drawn into the cylinder. 

In the horizontal machine, the valves are like those 
used in the consolidated compressors, the stems and disks 
being of forged steel set in cast-steel housings. Lift 
of the valves is given by cushion springs and controlled 
by compression springs and the suction valves are of the 
Featherstone safety type so that it is impossible for them 
to fall into the cylinder. The piston is screwed to the 
piston rod by a jam nut, and the connecting rod is pro- 
vided with adjustable wedges for taking up the wear of 
the boxes. 

In a double-acting, ammonia compressor, the stuffiing- 
box is one of the most vital parts. Referring to Fig. 
177, letters A, B, C, D, E and F indicate composition 
split packing rings and letters Q, R, S, U, V and W de- 
note pure tin rings of an inside diameter 1-16 inch larger 
note that of the piston rod. These rings should never be 
split. 

/ is a lantern which forms an oil storage reservoir in 
the stuffingbox, the oil being taken in at the point marked 
K from a pipe connected to the oil trap. This passage 
being always open, the oil is forced into the stuffingbox 
by the high pressure of the gas in the oil trap, thus 
keeping the lantern full and instantly replacing what 



EEFKIGERATION 



465 




466 



ENGINEERING 




FIGURE ITS. SECTION OF THE DA8HP0T. 




FIGURE 179. RETURN BEND FOR THE ATMOSPHERIC CONDENSER. 



REFRIGERATION 467 

little oil is carried into the cylinder by the rod. L is a 
lantern which at the point marked M has a pipe con- 
nection to the suction line so that any ammonia gas which 
may have escaped the packing rings, C, D, E and F is 
drawn back. By this device, packing rings A and B 
have to withstand only the suction pressure. A^ is the 
stuffing-box gland which h^s a chamber supplied with oil 
through O from a small rotary oil pump operated from 
the main shaft. P is the oil gland which should be kept 
just tight enough to keep the oil in the stuffingbox gland. 

Points of contact with the rod are G, H and / and 
they are made an exact fit. If the rod becomes scored 
and is turned down, these parts must be rebabbitted. To 
tighten the stuffingbox gland it is only necessary to ad- 
just the nut T, which is a pinion nut and is in mesh with 
the inside gear and the other two pinion nuts. 

As shown in Fig. 178, the dashpot is of a special 
design and allows for the adjustment of both vacuum 
and cushion. It is placed on an extension of the cylin- 
der foot and connected by the usual vertical link rod 
to the crank on the valve stem. The central cylinder A 
acts as a guide and piston while the pot B rises and falls 
and by so doing draws air into the chamber C through 
the passage D, the vacuum C being regulated by the 
position of the needle valve E. As the pot falls, air 
escapes from C through valve H and the fall is free 
until the lower end of the pot cushions into a chamber K 
formed by drawing up the ring F by means of the screw 
G. The position of F determines the amount of the 
cushioning and the leather washer R prevents hammer- 
ing at the end of the fall. 



468 



ENGINEERING 



DOUBLE-PIPE AMMONIA CONDENSER. 

This type of condenser consists of two series of coils, 
one within the other, and is usually built m four differ- 
ent forms having 2-inch and 1.25-inch, 2.5-inch and 1.25- 
inch, 3-incL and 2-inch pipes or, having the upper out- 
side pipes 2.5 inches and the lower pipes with all of the 
inner pipes 1.25 inch. Of these forms, the first is used 
most extensively, but the second is used whenever extra 
strong pipe is required and the third when extremely 
dirty water is to be handled. The ammonia circulates 
downwards through the annular space between the two 




FIGURE 180. DOUBLE-PIPE RETURN BEND. 

sets of pipe coils. By this arrangement a compara- 
tively" small charge of ammonia is required, owing to 
the narrowness of the space between the pipes. 

Occupying small space, the condenser can be placed 
in a basement or other convenient place. Since the flow 
of ammonia gas and the cooling water are in opposite 
directions, the hottest gas comes in contact with the 
hottest water and thus fully utilizes the cooling effect of 
the water. 

Figure 179 shows a sectional view of the atmospheric 
condenser return bend and Fig. 180 a view of the return 



REFRIGERATION 



469 




470 



ENGINEERING 




o 
o 

« 

w 



REFRIGERATION 471 

bend which is used for the double -pipe ammonia con- 
denser and also for the brine cooler. Figure i8i shows 
the double-pipe condenser in which, owing to the con- 
struction of the return bend, it is possible to remove 
and replace any length of pipe without tearing down the 
whole coil as is necessary where double-pipe connections 
are made with screwed bends. 

Condensers are furnished complete with gas, liquid, 
pump out, and water headers and one of the special 
features is the construction of the liquid and purge head- 
ers which are made with special tee valves. Owing to 
the design, additional sections can be added at any time 
as enlargement of the plant may require. 

Figure 182 shows a double-pipe brine cooler which is 
built on the same general plan as the ammonia con- 
denser, but is made of 2 and 3-inch pipes. Liquid am- 
monia enters and is expanded in the bottom pipe and the 
gas is drawn oft at the top, while the brine is pumped 
into the top and circulates downward, through the an- 
nular space between the two pipes. 



472 



EN-GINEEEING 




REPRIGERATIOK 



473 




474 QUESTIONS 

1. Of what does the process of refrigeration consist? 

2. Describe a freezing mixture that will give a tem- 
perature of 67° below zero. 

3. Upon what are the theory and practice of mechan- 
ical refrigeration based? 

4. What are the two first laws of thermo-dynamics ? 

5. Can the quantity of heat in the universe be increased 
or diminished ? 

6. What is the result of compressing a pound of air 
at 70° temperature, and atmospheric pressure, to one- 
half its original volume ? 

7. In order that the higher pressure may be maintained 
as the temperature is reduced, what is necessary? 

8. If the pound of compressed air be allowed to ex- 
pand in a cylinder what will be the result? 

9. What can be said of the mechanical work done by 
this air in its expansion? 

10. What can be said of the distribution of heat 
throughout the universe? 

11. How is the temperature of a body or substance 
reduced ? 

12. What work is demanded of a refrigerating ma- 
chine ? 

13. How may a refrigerating machine be defined, and 
what is its main function? 

14. How may the various devices for refrigeration 
and ice making be classified? 

15. How is refrigeration accomplished in apparattts 
belonging to the first class ? 

16. Describe the vacuum system. 

17. How is refrigeration effected in machines belong- 
ing to the third class? 

18. Describe the absorption system. 



ENGINEERING 475 

19. How IS refrigeration effected in machines belong- 
ing to the fifth class? 

20. What two systems have come into general use in 
this country? 

21. What are the three distinct stages, in the com- 
pression system? 

22. What is the refrigerating medium used in this 
process or system? 

23. Of what does ammonia consist, and what is its 
chemical formula? 

24. Under what two conditions may gaseous ammonia 
be liquefied? 

25. To what pressure is the gaseous ammonia usually 
compressed ? 

26. In order to liquefy gaseous ammonia by cold, what 
temperature is required? 

2y, What takes place during compression? 

28. How is the vapor condensed and liquefied ? 

29. How are the refrigerating qualities of the ammo- 
nia in its liquefied state utilized? 

30. After being expanded into vapor what becomes 
of it? 

31. How many, and what are the systems of refrigera- 
tion by compression? 

32. Describe the theory of the 'Vet" system as ef- 
fected in the action of the Linde machine. 

33. Upon what does the pressure of steam in a boiler 
depend ? 

34. What are the relations of the temperatures of the 
steam, and the water from which it was generated, so 
long as they are in contact ? 

35. What is the result if the steam be superheated? 

36. What results from the compression of a dry gas 
without cooling? 



476 QUESTIONS 

37. What does the Adiabatic curve as traced by the 
indicator represent? 

38. How is the cooHng of the vapor accomphshed in 
the Linde compressor? 

39. Describe in brief the construction of the cyhnder 
heads, piston, and valves of the Linde ice machine. 

40. What is the clearance between piston and cylinder 
head? 

41. How is the piston lubricated? 

42. What may be said of the area of the valves in the 
Linde machine? 

43. Describe briefly the stuffing box of the Linde 
machine. 

44. How many methods are there of utilizing re- 
frigeration ? 

45. Describe the Brine system. 

46. Describe the direct expansion system. 

47. Which one of the two systems is the more efficient ? 

48. Mention a few of the advantages that the direct 
expansion system has over the Brine system. 

49. By what two systems is ice made, or manufac- 
tured ? 

50. Describe in general terms the can system of ice 
making. 

51. In the De La Vergne refrigerating machine how 
is the heated gas cooled? 

52. Mention a characteristic feature of this machine. 

53. What are some of the advantages claimed for the 
De La Vergne machine ? 

54. Describe the action of the valves in the De La 
Vergne machine. 

55. Describe in general terms the course of the am- 
monia in this machine and apparatus connected with it. 



ENGINEFEIN0 477 

56. Describe briefly the course of the oil used for 
seaHng, and other purposes, in the De La Vergne ma- 
chine. 

57. How many valves has the Triumph ammonia com- 
pressor ? 

58. What advantage is gained by the use of the third 
or auxihary suction valve? 

59. Describe in brief the construction and action of 
the valves in this machine. 

60. What other agents besides ammonia are employed 
in the compression systei) of refrigeration? 

61. By whom was th^ 'bsorpt^'cn system of refrigera- 
tion invented? 

62. What chemical action is involved in this process? 

63. How many distinct sets of appliances are re- 
quired ? 

64. Mention the functions of each. 

65. What advantage appertains to the absorption sys- 
tem of refrigeration? 

66. What pressure is maintained in the generator? 

67. Describe in general terms the operation of an ab- 
sorption device. 

68. Is power required in its operation? 

69. What is done with the air escaping from the ab- 
sorber in Carre's apparatus? 

70. Describe the operation of Recce's device for re- 
frigeration by absorption. 



CHAPTER 



j\^^. 



CORLISS ENGINE VALVE GEAR. 

Fig. 185 shows the valve gear of a CorHss Engine. 
A^ shows the connection of the steam pipe with the steam 




FIG. 185. VALVE GEAR OF A CORLISS ENGINE. 

chest on top of the cyHnder, and E^ is the exhaust pipe 
underneath. There are four valves, two steam admis- 

478 



CORLISS VALVE GEAR 47S 

sion valves above, and tvv^o exhaust valves beneath. These 
valves are all of the rotative type, extending across the 
entire width of the steam chest on top, and the exhaust 
chest directly under the cylinder. The working face of 
a Corliss valve is turned to a true circle, and the seat in 
which the valve works is bored to a true circle also, and 
is fitted with ports. The valves are rotated part of a 
revolution at each stroke of the piston, motion being 
transmitted to them through the medium of the wrist 
plate W, and the rods M-N-O-Q. The wrist plate re- 
ceives its vibratory motion from the eccentric by means 
of the rod E. The valves are fitted with cranks 
M^-N^-O^-Q' to which the rods M-N-O-Q are con- 
nected. These rods are threaded on the ends in order 
that their lengths may be varied, when necessary in ad- 
justing the valves. 

The connections of the exhaust valves to the wrist 
plate are positive, the travel of these valves being a fixed 
quantity. 

The connections of the steam valves with the motion 
of the wrist plate are detachable, the travel of these 
valves being under the control of the governor, when the 
engine is running up to speed. R-R are the ends of the 
exhaust valves, to which the cranks O^ and Q' are keyed. 
A shows the end of one of the steam valves. X is a crank 
arm that is keyed to the valve spindle or stem. D and D' 
are the dash pots. F-F are the dash pot rods that con- 
nect the arms X-X of the valves with the dash pots. The 
Cranks M^-N^ rotate loose upon the valve spindles, in fact 
they are loose sleeves, carrying arms C-C at right angles 
to M^N'. These arms C-C also carry at their free ends 
trip hooks L-L that engage the blocks B when the arms 



480 



ENGINEEEING 




CORLISS VALVE GEAR 



481 



are at the lowest point of their travel. The engagement of 
the trip hook with the block B, and the lifting of the arm 
C, causes the steam valve to rotate upon its seat and un- 
cover the steam port for the admission of steam to that 
end of the cylinder. The steam valve does not open wide 
only when the engine is being started, or before full speed 
has been attained. This is owing to the fact that the gov- 
ernor controls the position of the trip mechanism J-K, 




FIG. 187. CROSS COMPOUND CORLISS ENGINE. 



which also turns freely on the stem or spindle of the 
valve. The point J of this mechanism is brought to bear 
upon the arm of the trip hook L by the governor through 
the arm K and rod H thus causing the hook to becom.e 
disengaged from the block B, allowing the arm X to 
drop and close the valve. This closure of the valves 
is accomplished quickly, owing to the constant pull down- 
wards of the dash pots on the arms XX. The dash pots 
are simple cast iron cylinders, open at the top, and fitted 



482 



ENGINEERING 



With air tight pistons to which the rods F-F are con- 
nected. The Hfting of these pistons by the arms XX 




FIG. 188. HORIZONTAL-VERTICAL CORLISS ENGINE. 



causes a vacuum under the pistons, and the pressure of 
the atmosphere upon the top surface of the pistons causes 
them to drop quickly. 



HIGH SPEED ENGINE 483 

HIGH SPEED, HORIZONTAL, PISTON-VALVE 
ENGINE 

In Fig. 189 is shown the latest type of horizontal en- 
gine manufactured for direct connection to electric gen- 
erators. With slight modifications these engines can be 
operated independently. 

An automatic governor effects close regulation and 
large bearing surfaces, together with forced lubrication 
and light parts, adapt the engine for high speed operation. 
An oil pump operated by the crank shaft draws oil from 
the reservoir in the base of the engine and forces it 
through pipes and internal passages in the moving parts 
to the main bearings, the crank pin, the crosshead pin 
and the guides, valve slide and eccentric. 

Oil is thus supplied at a pressure of 15 pounds per 
square inch, so that a thin film of lubricant is maintained 
between the metal surfaces, and by preventing contact 
reduces friction and wear. This system of lubrication, 
together with the complete enclosing of the parts, results 
in a mechanical efficiency of something over 90 per cent 
and permits the engine to be run continuously with little 
or no supervision. 

To prevent oil entering the cylinder on the piston rod 
and at the same time to make it impossible for water 
formed in the stuffingbox to get inside of the easing, a 
water-shed partition with a bronze stuffingbox is in- 
serted in the frame a few inches from the cylinder and 
is so constructed as to leave the cylinder stuffingbox 
easily accessible. 

Although enclosed for protection from dust and dirt, 
the moving parts can be examined by means of openings 



484 



ENGINEERING 




HIGH SPEED ENGINE 



485 



In the crank case which are covered with oil-tight plates. 
If necessary or desirable, the entire case can be removed. 




FIG. 190. VALVE CHEST WITH COVER REMOVED. 

To minimize power expended for operation, the steam 
valve, which is of the double-ported piston type, is bal- 
anced, and since it works in a renewable bushing and has 




FIG. 191. PARTS OF THE ECCENTRIC AND THE VALVE. 



cast-iron packing rings turned to an exact fit, the valve 
is easily kept steam tight. Figure 190 shows the valve 
casing with the outside plates removed. 



4^6 ENGINEERING 

In the flywheel is an automatic Rites governor to which 
an eccentric is attached and connected by a rod to the 
steam valve, thus giving the motion for correct steam 
distribution. Figure 191 show^s the eccentric and its 
connecting rod, as well as the piston valve and rod. 

Cutoff ranges from o to three-fourths stroke and the 
speed is so regulated, by automatically altering the point 
of cutoff, that the variation from no load to full load 
is not more than 1.5 per cent. To reduce condensation, 
the casting forming the cylinder and valve chest is heav- 
ily lagged with magnesia and asbestos of good quality, 
held in place by a cast-iron casing of neat design. At 
each end of the cylinder is a relief valve to guard against 
damage from water in the cylinder and adjustable to 
open at any desired pressure. 

Taps for connections of indicator piping are m.ade in 
the cylinder. To secure lightness and strength, the cast- 
iron piston is cored out and provided with internal ribs, 
being fastened to the piston rod, which is forged from 
open-hearth steel, by forcing it on a taper and securing 
it with a nut and pin. 

Moving in guides cast in one piece with the engine 
frame, the crosshead is equipped with adjustable cast- 
iron slippers to allow for wear and is provided with a 
steel crosshead pin flattened on two sides. At the crank- 
pin end the connecting rod of forged steel has a cast-iron 
box lined with white metal, which is hammered in and 
accurately bored. At the crosshead end it is provided 
with a steel strap, an adjustable key, and a bronze box. 
Counterweights are secured to the webs of the crank 
shaft and the engine is finished in a thorough manner. 



HIGH SPEED ENGINE 



487 




488 ENGINEERIN^G 



AIR COMPRESSORS. 

COMPOUND AND MULTIPLE STAGE AIR COM- 
PRESSION. 

Compression of gas is accomplished generally by one 
of the two methods technically termed adiabatic, with- 
out transference of heat, no heat is removed from the 
gas, and a consequent rise of temperature attends the 
operation, a diagram indicating the line of compression 
will demonstrate the resulting loss of power due to not 
extracting the heat generated by compression, as the 
volume is greatest in adiabatic compression, and in ratio 
increasing with pressure, and isothermal, wherein the 
heat developed by compression is carried away as fast as 
generated. 

Water jacketed air or gas cylindeis are provided for 
both compressions mentioned above, but contact between 
the vapor and cooling medium is transient, resulting in 
inconsiderable benefit, referring to abstraction of heat, 
and mainly effective in reducing temperature of cylinder 
walls, therefore, most economical operation will follow 
multiple stage compression and by withdrawing the heat 
thereof by a suitable cooling medium and apparatus, and, 
as fast as developed, in compounding, compression is car- 
ried forward in the first cylinder adiabatically or without 
the abstraction of heat, practically, the cylinder walls 
being cooled by' a circulating fluid, compression is not 
accomplished in the initial cylinder to a high pressure, 
ancj a device intervenes between the first and second 
cylinders, through which the vapor passes to fimal com- 
pression, termed an inter-cooler, and, provided this de- 
vice is properly designed and constructed, and furnished 



AIR COMPRESSORS 489 

with a cooling medium adequate in quantity and of suffi- 
ciently low temperature, heat of compression is with- 
drawn until approximately the initial temperature is had 
and the volume reduced. 

An after-cooler may be employed with profit in effect- 
ing a reduction of heat after final compression, and in 
abstracting moisture from the air or gas, furthermore 
an advantage accrues therefrom during operation in cold 
weather, especially where the air discharge line is ex- 
posed, by preventing an accumulation of frost upon the 
inside walls thereof. 

Lubrication is more easily accomplished in two-stage 
than in single stage compression, vaporizing of the lubri- 
cant is not so rapid, resulting in more effective service 
and less deterioration of the wearing parts. The danger 
of explosion, while rarely attending adiabitic compression 
of air, is further removed under two-stage operation. 

The volumetric efficiency of the machine is improved 
in that the terminal pressure in the first cylinder is lower 
than the final pressure under single stage compression, 
and the inflow of air begins at an earlier period of the 
return movement of the piston by reason of the fact that 
the expansion of the air or gas in clearance space occu- 
pies a reduced space in the cylinder. 

Compressors of special type for a maximum of 3,000 
pounds per square inch are furnished. 

For pressures exceeding 100 pounds per square inch, 
for economy and safety compounding is recommended, 
for pressures exceeding say 400 pounds per square inch, 
multi-stage compression. 

For pressures under 100 pounds per square inch, fac- 
tors must enter into consideration upon which local con- 
ditions have a bearing, first cost, comparing cost of in- 



490 ENGINEERING 

stallation of single and two-stage machines, cost of fuel, 
horse power developed. 

The table of horse powers developed under multi-stage 
compression is upon the following basis: Water- jacketed 
cylinders with temperature of air reduced to 60 degrees 
Fahrenheit in the inter-coolers. Atmosphere at 60 de- 
grees. Three per cent approximatel}^ allowed for friction 
of piston for each cylinder. 



ELECTRIC COMPRESSORS 

SINGLE AND MULTIPLE STAGE 

A special design of compressor, suitable for motor 
drive, is shown in Fig. 193 or may be modified into a 
steam actuated unit and for air pressures ranging from 
eighty to twenty-five hundred pounds per square inch. 
The unit here showm is as constructed for a working 
pressure of 2,500 pounds per square inch, and tested to 
3,000 pounds per square inch, operating at 560 revolu- 
tions per minute. 

Its compactness will render its installation possible in 
a space entirely too small for regular types, space re- 
served in high buildings for the power plant, mines, ship- 
board ; the speed of operation is favorable in many in- 
stances to direct connection to motors. 

For developing a pressure of eighty pounds or less, 
and in instances where multi-stage compression is not 
desired, four air cylinders of equal diameter may be in- 
stalled, if multi-stage is desired, one or more initial air 
cylinders are employed and compounding or multi-staging 
provided for, and up to a terminal pressure of 2,500 
pounds, with inter- and after-coolers. 



AIR COMPRESSORS 



491 




*l 



'\ a 



492 ENG1NEERIN"G 

In the selection of material entering into the con-itruc- 
tion thereof, great care has been taken to provide metals 
of uniform texture, of great strength, and of kinds best 
adapted for servir-. imposed, and without regard to cost. 
For the maximum pressure, second, third, and fourth 
stage air cylinders are provided, with inter-coolers of 
very liberal cooling surfaces, and an after-cooler. The 
main bearings are automatically lubricated, the oil pump 
therefor being actuated by a reciprocating part of the 
machine and a device provided for automatically cooling 
and screening the lubricant. A cooling water pump is 
also attached, providing circulating w^ater for air cylin- 
ders and inter-coolers. 

Air valves are of special design permitting of the speed 
mentioned above, and quiet operation. 

Special lubricators are provided. 

AIR COAIPRESSOR GOVERNOR 

Where a steam driven single air compressor, or a com- 
pressor driven by a constant speed motor, is used to fur- 
nish air in varying quantities, some method other than 
the extremely wasteful one of allowing the surplus air 
to escape through a safety valve should be used. By 
preventing the atmosphere from entering the cylinder 
the compressor cannot do any work, consequently can- 
not consume power, although running at full speed, be- 
yond that required to keep the machine alive, or rather 
to overcome the unloaded frictional resistance. xA.n 
automatic valve for accomplishing this is showm in cut. 
It is simply a balanced governor valve controlled by a 
pilot valve. A small pipe leads from the air receiver to 
the pilot valve. The weight or spring, or both, may be 



AIR COMPRE'^KORS 



493 



regulated to allow the valve to unload at any pressure 
desired. With a slight fall in the receiver pressure it 
will gradually allow the air to enter the cylinder, there- 
by giving the compressor its load again. 




FIG. 194. AIR COMPRESSOR GOVERNOR. 



This device loads and unloads very gradually, giving 
the compressor time to receive its load without shock; 
is noiseless in its operation, and is ver\ close in its reg- 
ulation. 



494 ENGINEERING 

DIRECTIONS FOR SETTING AND OPERATING 
AIR COMPRESSORS 

Foundation. It should be the first care in instalHng 
an Air Compressor to provide it with a suitable founda- 
tion. The Compressors are self-contained and need 
foundations only of such design and strength as will in- 
sure the compressor remaining rigidly in place, a poor 
foundation costs almost as much as a •good one, and as 
a compressor is usually a permanent fixture, it is advisable 
to put in a good foundation. 

Blue prints are usually furnished showing location and 
proper size of foundation bolts for each machine, from 
which a template can be made by which the foundation 
bolts can be accurately located. It is of great importance 
that space should be left around foundation bolts so that 
they may be left free to move. The setting of the com- 
pressor is rendered much easier by taking this precaution. 
A good way to do is to put a short piece of pipe around 
each foundation bolt, carrying it up with the foundation, 
thus leaving the desired space behind it. In case a con- 
crete foundation is installed, the pipe should be full length 
around each rod. 

Setting Compressor. After the compressor has been 
placed in position, block the compressor off the founda- 
tion about J4 ii^ch by means of iron wedges, upon which 
the compressor should set level. Then the cement should 
be run into the bolt holes and also between the base of 
the compressor and foundation to insure true bearing all 
around. 

Pipe Connections. The steam and exhaust pipes 
should be as free from L's as possible, and only should be 



AIE COMPRKSSORS 



495 




496 ENGINEERING 

used in so far as is demanded by expansion of pipes. All 
pipes should be thoroughly cleaned before starting the 
compressor, so that metal chips from cutting pipes may 
not be carried into the steam chest and score the valves 
and seats. 

Proper allowance should be made for the expansion 
of the steam pipes in connecting same up. 

A drain pipe or bleeder should be provided for live 
steam, connection being made directly above throttle 
valve and with the drain, so that the water of condensa- 
tion may not have to pass through the steam cylinders. 
If steam connection for compressor is taken from main 
steam line instead of direct from boilers, the connection 
should be taken from the top of the steam pipe, thus 
avoiding the carrying of condensation. 

The cocks and drains provided for both steam and air 
ends should be opened after the pump ceases operation, 
so that the water may be thoroughly drained, thereby 
avoiding any possibility of freezing. 

In connecting water pipe to jacket around air cylinder 
care should be exercised to allow for proper drainage of 
cooling surface and pipes. In cold weather the water 
should be drained or breakage from freezing might occur 
in cylinder or jacket. 

In piping air discharge pipe use lead in all joints and 
screw up tight, as air leaks are expensive. 

Packing. After all connections are made and com- 
pressor is ready to start, fill the rod and steam valve stem 
stuffing boxes with a good grade of packing. Cut the 
packing so that it will fit easily in stuffing boxes. Do not 
pound it in and be careful that no grit is carried in with it, 
so as to mar the piston rod. When tightening the gland, 
remember that a gland should only be tight enough to 



AIB COMPRESSORS 



497 




498 EXGIXEERING 

prevent leakage. If the gland is too tight it will cause 
undue friction and also may score and cut the rod. 

Receiver. The air receiver should be so constructed 
so that the discharge pipe from the air compressor enters 
at top and goes to within six inches of the bottom of the 
receiver. The outlet pipe from the receiver should be on 
the side near the top. 

Gexer.\l Precautions. Before starting the com- 
pressor, clean out all oil holes and grooves and see that 
all bearings are properly adjusted. Go over the com- 
pressor and see that all bolts and screws and nuts are 
thoroughly tightened, and it is advisable after the ma- 
chine has been in operation for several hours to repeat 
the above operation in order to insure that nothing has 
worked loose. 

When locating the compressor place it in a position or 
so locate the air induction pipe that it will have plenty of 
clean air. If the machine is placed in a position where 
fine particles of dust are floating in the air, the air valves 
are liable to become choked up and stick. Other parts 
of the compressor, such as slides, valves, stems, etc., are 
liable to undue wear when subjected to grit from the 
surrounding air. 



AIR COMPRESSORS 



499 



Contents of Cylinder 


IN Cubic 


Feet For Each 






Foot in Length. 






Diameter 


Cubic 


Diameter 


Cubic 


Diameter 


Cubic 


in Inches. 


Contents. 


iu Inches. 


Contents. 


in Inches. 


Contents. 


1 


.0055 


8% 


.4175 


21 


2.405 


\% 


.0085 


9 


.4418 


21% 


2.521 


1% 


.0123 


9M 


.4668 


22 


2.640 


1% 


.0168 


9X 


.4923 


22% 


2.761 


2 


.0218 


9% 


.5185 


23 


2.885 


1% 


.0276 


10 


.5455 


23% 


3.012 


2% 


.0341 


10% 


.5730 


24 


3.142 


2% 


.0413 


10% 


.6013 


25 


3.409 


3 


.0491 


10% 


.6303 


26 


3.687 


3>i 


.0576 


11 


.6600 


27 


3.976 


3X 


.0668 


11% 


.6903 


28 


4.276 


3% 


.0767 


11% 


.7213 


29 


4.587 


4 


.0873 


11% 


.7530 


30 


4.909 


4J^ 


.0985 


12 


.7854 


31 


5.241 


4X 


.1105 


12% 


.8523 


32 


5.585 


4% 


.1231 


13 


.9218 


33 


5.940 


5 


.1364 


13% 


.9940 


34 


6.305 


5>i 


.2503 


14 


1.069 


35 


6.681 


5>^ 


.1650 


14% 


1.147 


36 


7.069 


5% 


.1803 


15 


1.227 


37 


7.468 


6 


.1963 


15% 


1.310 


38 


7.886 


6% 


.2130 


16 


1.396 


39 


8.296 


6X 


.2305 


16% 


1.485 


40 


8.728 


6% 


.2485 


17 


1.576 


41 


9.168 


7 


.2673 


17% 


1.670 


42 


9.620 


7% 


.2868 


18 


1.767 


43 


10.084 


7X 


.3068 


18% 


1.867 


44 


10.560 


7% 


.3275 


19 


1.969 


45 


11.044 


8 


.3490 


19% 


2.074 


46 


11.540 


8>i 


,3713 


20 


2.182 


47 


12.048 


8X 


.3940 


20% 


2.292 


48 


12.566 



500 



ENGINEERING 



Horse-Power Developed — To Compress 


100 Cubic 


Feet Free Air From Atmosphere 


TO 




Various Pressures. 




Gauge 
Pressure 
Pounds. 


One-Stage 

Compression 

D. H.P. 


Gauge 
Pressure 
Pounds. 


Two-Stage 

Compression 

D. H.P. 


Four- St age 

Compression 

D.H.P. 


10 


3.60 


60 


11.70 


10.80 


15 


5.03 


80 


13.70 


12.50 


20 


6.28 


100 


15.40 


14.20 


25 


7.42 


200 


21.20 


18.75 


30 


8.47 


300 


24.50 


21.80 


35 


9.42 


400 


27.70 


24.00 


40 


10.80 


500 


29.75 


25.90 


45 


11.14 


600 


31.70 


27.50 


50 


11.90 


700 


33.50 


28.90 


55 


12.67 


800 


34.90 


30.00 


60 


13.41 


900 


36.30 


31.00 


70 


14.72 


1000 


37.80 


31.80 


80 


15.94 


1200 


39.70 


33.30 


90 


17.06 


1600 


43.00 


35.65 


100 


18.15 


2000 
2500 
3000 


45.50 


37.80 
39.06 
40.15 



AIR COMPRESSORS 



501 



Table 


OF Effic 


[KNCiKS AT Different Altitudes. 


Altitude 
in 

Feet. 


BAROMETRIC PRESS URK. 


Volumetric 

Efficiency 

of 

Compressor, 
Per Cent. 


Loss of 
Capacity, 
Per Cent. 


Decreased 

Power 
Required, 
Per Cent. 


Inches 
Mercury. 


Ponnds ]m^.t 
«<i. 111. 





30.00 


14.75 


100 








1000 


28.88 


14.20 


97 


3 


1.8 


2000 


27.80 


13.67 


93 


7 


3.5 


3000 


26.76 


13.16 


90 


10 


5.2 


4000 


25.76 


12.67 


87 


13 


6.9 


5000 


24.79 


12.20 


84 


16 


8.5 


6000 


23.86 


11.73 


81 


19 


10.1 


7000 


22.97 


11.30 


78 


22 


11.6 


8000 


,22.11 


10.87 


76 


24 


13.1 


9000 


21.29 


10.46 


73 


27 


14.6 


10000 


20.49 


10.07 


70 


30 


16.1 


11000 


19.72 


9.70 


68 


32 


17.6 


12000 


18.98 


9.84 


65 


35 


19.] 


13000 


18.27 


8.98 


63 


37 


20.6 


14000 


17.59 


S.65 


60 


40 


22,1 


15000 


16.93 


8.32 


58 


42 


23.5 



502 



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AIR COMPRESSORS 



505 



Mean Effective Pressures.* 


For the Compression Part only of the Stroke when Com- 


pressing and Delivering Air from One Atmosphere 


to Given Gauge-Pressure in a Single Cylinder. 


Gauge 


Adiabatic 


Isothermal 


Pressure. 


Compression. 


Compression. 


1 


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2 


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3 


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5 


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80 


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35 


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40 


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11.7 


45 


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12.62 


50 


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13.48 


55 


15.98 


14.3 


60 


16.89 


15.05 


65 


17.88 


15.76 


70 


18.74 


16.43 


75 


19.54 


17.09 


80 


20.5 


17.7 


85 


21.22 


18.3 


90 


22. 


18.87 


95 


22.27 


19.4 


100 


23.43 


19.92 



*The Mean Effective Pressure for compression only is always lower than 
the Mean Effective Pressure for the whole work. 



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QUESTIONS ON COMPOUND AND MULTIPLE 
STAGE AIR COMPRESSION. 

1. How many systems of gas compression are usually 
employed ? 

2. How are they designated? 

3. Explain the principles underlying the Adiabatic sys- 
tem. 

4. What is the leading characteristic of the Isother- 
mal method? 

5. How are the compressor cylinders cooled? 

6. What is the most economical system of compres- 
sion ? 

7. Describe it briefly. 

8. Mention several advantages possessed by multiple 
stage over single stage compression. 

9. Upon what basis is the table of horse-powers de- 
veloped under multiple stage compression computed? 

10. How many pounds pressure per square inch may 
a motor driven high speed air compressor be safely 
operated at? 

11. How many stages of compression are usually 
provided for the very high pressures? 

12. How is lubrication of the apparatus accomplished? 

13. Describe the method of controlling the quantity 
of air compressed. 

14. What is an air compressor governor? 

15. What should be the first care in setting up an air 
compressor ? 

508 



QUESTIONS 509 

i6. Describe the best method to pursue in regard to 
foundation bolts. 

17. Describe the proper method of setting a com- 
pressor. 

18. What rule should be followed regarding the pip- 
ing? 

19. Where should the drain pipe for live steam be 
located ? 

20. What rule should be observed regarding the steam 
connection for the compressor!^ 

21. What regulations should be adhered to in con- 
necting the water pipes? 

22. Describe the proper method of packing the piston 
rods of an air compressor. 

22), How should the air receiver be constructed? 

24. What are some general precautions to be ob- 
served ? 

25. What special precaution should be taken regard- 
ing the air induction pipe? 



CHAPTER XII. 

PUMPS. 

All engineers have more or less dealing with pumps 
of some type, and it is proper that a short space be de- 
voted to a study of the principles governing the action 
of a pump, and especially that law of nature which 
makes it possible to raise water from a lower level to 
a higher plane, by the pressure of the atmosphere upon 
the surface of the water to be raised. A pump may be 
described in general terms, as a device for Hfting liquids, 
and also for causing them to flow through pipes in such 
a manner that they will not return, therefore there must 
be a system of valves that will allow the passage of the 
liquid only in one direction. Water is the liquid with 
which we will deal, and the valves will all be required 
to act under the influence of the currents passing through 
them without the assistance of outside rods or other 
appliances. In other words they must be automatic. In 
Figure 198 three kinds of non return valves are shown, 
and a short description of each will serve to give the 
student a fair idea of their action; a a is a section of a 
vertical pipe in which there is fitted a cross diaphragm 
with a hole in it. This forms the ''seat" of the valve 
b, which is hinged at c. The hole in the diaphragm may 
be circular, rectangular, or any other shape, but the plate, 
or valve b must be large enough to cover it, and its 
under surface, and the raised rim or seat upon which 
it rests must be trued up to fit each other water tight. 
It is evident that if water is forced up through the pipe, 
510 



PUMPS 



511 



it will push the valve b open, and pass through the hole, 
but will not be able to return, for the reason that just 
as soon as the upward current ceases, the valve will 
close by its own weight, and thus retain the water that 
has passed through it. In the second form of valve, 
d d is a section of vertical pipe, having a diaphragm, 




FIGURE 198. 



in which a circular conical hole is bored. A conical disk 
e which is the valve, is turned to fit this opening or 
seat, and contact between the valve and seat is made 
water tight by grinding the valve in the seat with very 
fine flour of emery, followed up by ''crocus," which is 
chemically prepared oxide of iron. This form of valve 



512 ENGINEERING 

is fitted with a stem f, which passes above and below 
through holes in guide frames g and h, thus serving to 
always keep the valve in its proper axial position. The 
action of this valve is similar to valve b, in that it is 
opened by the rising current of water, and closed by its 
own weight, but its operation is much more satisfactory, 
being quicker and more delicate, as the water in rising 
passes up all around the valve, and in closing less water 
will pass the valve in the return direction for the reason 
that the valve closes more promptly. A third form of 
metal valve is shown at i i which is a section of pipe, 
with diaphragm, and valve seat. This type of valve is 
guided and held in its proper position by ribs 1 extending 
downwards, and having a loose fit against the sides of 
the circular passage below the seat. It is necessary that 
a stop be placed above the valve k to prevent its rising 
too high. The valves hitherto described are metallic. 
India rubber in various forms is more largely used for 
pump valves, than any other material. When a large 
volume of water at a high pressure is to be handled, the 
types of valves shown in Fig. 198 are not suitable, as 
their action is not quick enough, and the concussion 
caused by their closing is too severe. Many other types 
of metal valves have been designed, to obviate this shock, 
some consisting of a number of balls falling into spher- 
ical seats, others formed of rings of increasing diame- 
ter, each ring fitting as a valve to that beneath it, and 
forming a seat for the one above, while the top ring is 
closed by a small disk valve. Probably the best metal 
valve that has been brought out for this purpose is the 
double beat valve, shown in vertical section in Figure 
199. This valve is crown shaped in section, and has two 
faces, and two seats, an upper and a lower as shown, and 



PUMPS 



513 



over these the water passes, when the valve is open, in 
the directions indicated by the arrows a a and b b. The 
valve is guided in its movement by inside ribs, and a 
central stem. Under the collar of the latter, at c a leather 
washer is fitted to prevent concussion when the valve 
opens. The surface %)i the valve acted upon by the 
water, or acting upon it is the annular area comprised 
between the tw^o valve seats. Hence in proportion to the 




FIGURE 199. 



area of opening, a much greater pressure is exerted to 
overcome the resistance of the water in closing, than with 
any of the single seated valves. This force can, in fact, 
be made anything that is desired, for there is no limit to 
the ratios of the valve seats, until their diameters become 
equal, when the valve will be an equilibrium valve, and 
will not open to any internal pressure. The action of 
the valves being understood, the action of the various 
types of pumps may be easily comprehended. In Figure 
200 A is a vertical sectional view of the most simple 
form of lift pump, a is a pipe called the suction pipe, 



514 ENGINEERING 

rising from a well or other source of supply, and con- 
nected to the diaphragm which constitutes the bottom of 
the pump, and also forms the seating for the valve b, 
termed the suction valve. Above this valve is seen the 
pump cylinder or barrel, which is properly bored out, and 
in which moves the piston, or plunger c, having an open- 
ing through it guarded by the valve d. Both of these 
valves b and d open upwards, consequently the water 
can pass up through them, but cannot return. The 
plunger or piston c is connected to the forked end e of 
the pump rod f, and is packed with leather or other pack- 
ing so that it moves water tight in the cylinder. In order 
to thoroughly understand the principle governing the 
action of the pump it will be necessary to revert to the 
natural law referred to at the beginning of this chapter. 
This law is, that the atmosphere exerts a pressure of 
15 pounds (14.7 lbs. to be exact), per square inch upon 
all surfaces with which it comes in contact, therefore it 
will sustain a vertical column of water one square inch in 
area, and of such a height as to v^eigh 15 pounds. Now 
water at a temperature of 39.1° weighs 62.5 pounds per 
cubic foot, therefore a column of water one inch square 
and one foot high would weigh ^1=30.434 pounds. 
As the atmospheric pressure is 15 pounds per square 
inch, it follows that the column of water balanced by the 
atmosphere will be -~^ = 34.5 in height. These con- 
ditions assume that a perfect vacuum is created in the 
pump cylinder by the upward motion of the piston, but 
a perfect vacuum is practically impossible, at least in the 
pumping of water, owing to the fact that there is always 
air in water, which is released when the atmospheric 
pressure is removed from the surface of the water. 



PUMPS 



515 



The action is as follows, referring to Fig. 200. Sup- 
pose the pump piston c is at the bottom of the cylinder 
and just beginning the upward stroke. As it rises a par- 
tial vacuum will be created beneath it, as the air cannot 
pass down through the valve d, or past the packing that ^ 




FIGURE 200. 



is placed around u.- piston causing it to fit the cylinder 
water tight. 

Consequently the atmospheric pressure on the surface 
of the water in the well, being unbalanced by an equal 
pressure in the pump cylinder, forces water up through 
the suction pipe a, past the valve b, and into the pump 
cylinder, where it is retained by valve b. As the pump. 



516 ENGINEERING 

piston returns on the downward stroke, the valve d opens 
thus permitting the water in the cylinder to pass up 
through the piston, and on the next upward stroke, the 
valve d closes, and this water is lifted into the head g, 
of the pump, from whence it flows away through the 
pipe h. At the same time more water rises from the 
suction pipe a, through valve b, and fills the pump cylin- 
der underneath the piston. The height to which the pump 
will lift the water from the well, or rather to which the at- 
mospheric pressure will force the water, depends upon 
the character of the vacuum that is created in the cylinder 
by the up stroke of the piston. If there are no air leaks 
in the suction pipe, and the valves, piston, and cylinder 
are all properly fitted, a pump may be made to lift water 
28 feet. As before stated the atmosphere will, from a 
theoretical standpoint, sustain a column of water 34.5 
feet in height, but in pumping water there are certain 
unavoidable drawbacks to overcome, such for instance as 
the weight of the suction valve, or valves, the friction 
of the water in passing through the pipes, and the force 
required to raise the piston or plunger. This latter force 
will be equal to the weight of a column of water equal 
in diameter to the diameter of the pump piston, and in 
height to the distance from the surface of the water, 
to the underside of the pump piston. Therefore as the 
piston rises, an increasing force is required, the mean 
being that corresponding to the position of the bucket 
or piston at half stroke. Let P equal this force in pounds, 
d equal diameter of piston in inches, and h equal lift 
of water in feet, then P=.7854d^XhX434=.34d^h. 

Referring again to Fig. 200, B is a vertical section of a 
double acting force pump, in which d is the cylinder, c 
is a solid piston properly packed to fit the cylinder, f is 



PUMPS 517 

the piston rod, working through the stuffing box h. There 
are two suction inlets a a, guarded by valves b b, opening 
inwards, and g g are the discharge outlets, guarded by 
valves e e opening outwards. The action of this type 
of pump is as follows: When the piston moves down- 
wards, water enters the cylinder through valve b at the 
top, and the water below the piston is forcibly discharged 
through valve e, at the bottom. During the upward 
stroke of the piston, water is admitted through bottom 
valve b, and discharged through top valve e. When this 
type of pump is used for water, the force necessary to 
operate it may be found by the above formula, but h 
should equal the height in feet from the surface of the 
water at the source of supply, to the level to which it 
is forced. When the pump is used for air, the force to 
work it will be the pressure of air per square inch multi- 
plied by the area of the piston. 

A form of pump that is largely used for forcing water 
against high pressures, is shown in vertical section at 
C Fig. 200 in which f is the pump cylinder, within which 
moves the plunger h, which works water-tight through 
the stuffing-box i. 

Into the upper end of plunger h^ the pump rod k 
is secured. The pump here shown is single acting. C 
is the valve box or chamber, communicating with the 
pump cylinder through the passage d, a is the inlet, and 
b is the suction valve, through which the water passes 
as the plunger rises on the upstroke. When the plunger 
starts on the downward stroke, valve b closes, and the 
water is forced out through passage d, and discharge 
valve e into the delivery pipe g. In order that a water 
valve may be efficient it should be allowed sufficient lift, 
that is it should rise high enough to cause the area be- 



518 



ENGINEERING 



tween the valve and the edges of the seat, to equal the 
area of the opening through the seat. For a circular 
valve the area of opening will be 3.1416 r^ if r=the ra- 




dius. If h=the height of lift, the waterway between the 
valve and its seat will be 6.2832 r h. 

Hence if the valve is properly adjusted, its lift should 



PUMPS 519 

be not less than one-half the radius, thus 3.1416 r^=^ 
6.2832 r h, r=2 h. 

In a double beat valve, if r=the less, and r^ the greater 
diameter, the effective area of the opening is 3.1416 r^-, 
and the area of waterway given by the lift of the valve 

equals 6.2832 h (v-{-v^), therefore h= ^7^1)1/ ). A valve 

hinged on one side must be allowed to rise twice as high 
as one of the same size rising vertically, to give the same 
area of outlet. 

While there are various methods of actuating the water 
piston of a pump, it will hardly be necessary to devote 
much time, or space to any of these methods, except the 
two in which engineers are mainly interested, viz., steam 
pumps and power pumps. There is a large number of 
various types of steam pumps, each type having its own 
particular kind of steam valve, but only a few of the 
leading types will be noticed in this connection. 

Figure 201 is a sectional view of the Cameron steam 
pump, showing both the water end, and steam end. 
One of the leading features of this pump is, that there 
is no outside valve gear connected with the steam valve, 
this valve being operated entirely by internal appliances 
as will be understood by reference to Figure 202 w^hich 
gives an enlarged sectional view of the steam end. 

A is the steam cylinder; C, the piston; L, the steam 
chest ; F, the chest plunger, the right-hand end of which 
is shown in section ; G, the slide valve ; H, a lever, by 
means of which the steam-chest plunger F may be re- 
versed by hand when expedient ; // are reversing valves ; 
KK are the reversing valve chamber bonnets, and BE 
are exhaust ports leading from the ends of steam chest 



520 



ENGINEERING 



direct to the main exhaust and closed by the reversing 
valves //. 

The operation is as follows : 

C, the piston, is driven by steam admitted under the 
slide valve G, which, as it is shifted backward and for- 




riGURE 202. STEAM END OF CAMERON STEAM PUMP. 



ward, alternately connects opposite ends of the cylinder 
A with the live steam pipe and exhaust. This slide valve 
G is shifted by the auxiliary plunger F; F is hollow at 
the ends, which are filled with steam, and this, issuing 
through a hole in each end, fills the spaces between it 
and the heads of the steam chest in which it works. Pres- 



PUMPS 521 

sure being equal at each end, this plunger F, under ordi- 
nary conditions, is balanced and motionless, but when 
the main piston C has traveled far enough to strike and 
open the reverse valve /, the steam exhausts through the 
port E from behind that end of the plunger F^ which im- 
mediately shifts accordingly and carries with it the slide 
valve G, thus reversing the pump. No matter how fast 
the piston may be traveling, it must instantly reverse on 
touching the valve /. In its movement the plunger F 
acts as a slide valve to close the port E, and is cushioned 
on the confined steam between the ports and steam-chest 
cover. The reverse valves // are closed as soon as the 
piston C leaves them, by a constant pressure of steam be- 
hind them conveyed direct from steam chest through the 
ports shown by dotted lines. 

The arrangement of valves in the water end of this 
pump is shown in section in Figure 201. The right hand 
side is shown in full as it appears when the bonnet is 
removed, and the left hand side in section. 

By simply removing one bonnet or cover, the whole 
interior with every valve is plainly visible, turned inside 
out so to speak, and not a speck of anything that may 
have lodged there can escape detection. The shelves or 
decks are bored out tapering, and the brass seats forced 
in. They can thus be readily taken out and renewed at 
any time. Each stem holds two valves, with their springs 
one above the other, so that by simply unscrewing one 
plug, and pulling up the stem, both are released. It will 
be noticed that the Cameron valve chest is placed close 
to the ground and beside the water piston, instead of 
above it as in other makes. The valves are therefore 
just so much nearer the water, and the suction lift is 
reduced accordingly. Every pump has two suction open- 



5-22 



ENGINEERING 




PUMPS 



523 



ings, one on each side, and the discharge opening can 
be turned in any direction desired. 

Figure 203 is a full view of the Cameron pump as it 
appears when in operation. Figure 204 is a sectional 
view of the Dean steam pump. It will be noticed that 
ithere is an outside valve gear actuated by the piston 
'rod. Also that the water valves are above the water pis- 




FIGURE 204. DEAN STEAM PUMP SECTIONAL VIEW. 

ton. Figure 205 is a plan view of the Dean steam valve 
motion, the action of which is as follows : 

The auxiliary valve F slides on the valve seat E^, and is 
provided on its under side with diagonal exhaust cavi- 
ties d d.^ The ports b b^ and exhaust port c are arranged 
in the shape of a triangle, the diagonal cavities diverge 
from each other, whereby the cavity d connects the ports 
b and c, and cavity d^ connects the ports b^ and c when 
the valve F is in extreme positions. 



524 



ENGINEERING 



The operation is as follows: When the main piston 
moves from left to right the valve F is moved in an 
opposite direction, opening the port b^, admitting steam 
to the sub-cylinder E^ at the moment the main piston has 
reached the limit of its stroke, whereby the auxiliary 
piston E is forced to the left, opening the main port and 
admitting steam to the steam cylinder, consequently re- 
versing the movement of the main piston. On the return 
stroke of the main piston the movement of the auxiliary 
valve is reversed, whereby the port b^ is closed, and at- 
the moment the main piston has reached the limit of its 




FIGURE 205. PLAN VIEW OF DEAN STEAM VALVE. 

outer stroke, the port b is opened by the valve F, caus- 
ing the auxiliary piston E to reverse its motion, opening 
the main port and reversing the motion of the main 
piston. 

Figure 206 is a full view of the Dean steam pump, 
showing outside valve gear connections. 

The steam pumps hitherto described are what are 
termed single cylinder direct acting, that is, each pump 
has one steam cylinder and one water cylinder. 

A duplex steam pump consists of two water cylinders, 
and two steam cylinders, the steam valve of one side 
being actuated by the steam piston of the other, and 
vice versa. Figure 207 is a view of the Buffalo Duplex 



PUMPS 



525 



steam pump, and Figure 208 is a sectional view. The 
steam valves, of which there are two, are simple slide 
valves, each receiving its motion through the medium 
of a rocker arm, connected with the piston rod of the 
opposite side. 

The Worthington type of duplex steam pumps, and 
many others of the same class, have steam slide valves, 
actuated in practically the same manner. 




FIGURE 206. DEAN STEAM PUMP. 



The Epping Carpenter steam pump, of which Figure 
209 is an exterior view, is of the duplex pattern, and is 
fitted with piston steam valves. Figure 210 shows the 
^construction of this type of valve, described as follows: 

The valve is composed of the following parts : Body 
(A^. Followers (B), SoHd Rings (C), Self-adjusting 
Sings (D), Springs (E), Tongue Pieces (F), Valve Rod 
(G), Valve Rod Nuts (H), and Valve Rod Head (I). 



526 



ENGINEERING 



The self-adjusting rings (D) are split as shown, and 
the tongue piece (F) fitted into them, making them posi- 
tively steam tight in whatever position of travel. 

The rings (D) are made somewhat wider than the 
port openings in the lining, to prevent any gouging ac- 
tion when moving over the bridges, one side of the ring 
being always held around its entire circumference until 
the other side has passed the port opening. 




FIGURE 207. BUFFALO DUPLEX PISTON PATTERN PUMP. 



The rings (C) are made to a sliding fit and as they 
are solid will not compress under any pressure, making 
them of great value to stop momentum of steam pistons 
when cushioning. 

The outside adjustable valve motion, also illustrated 
in Figure 210, is made up of the following parts: 

Lost motion block link (K), Valve rod link head 
(L), Valve rod head pin (M), Lost motion block (N), 
Lost motion adjusting nuts (O), and Lost motion lock 
nuts (P). 

The lost motion block (N) is moved back and forth 



PUMPS 527 

on the lost motion block link (K) by means of a pin (R) 
attached to the crank on rock shaft, until it strikes the 
lost motion adjusting nuts (O), thus imparting motion 
to piston valve. 

Figure 211 shows a sectional view of the Epping Car- 
penter steam pump. It will be noticed that the water 
valves are above the water piston, thus keeping it con- 
tinually submerged. 

There are many other styles of steam pumps for the 
engineer to choose from, but space will not permit of 
their being described in this connection. 

A power pump is a pump, either horizontal, or ver- 
tical, in which the water piston is given a reciprocating 
motion, through the medium of a connecting rod, and 
crank driven by a belt, and gear wheels. 

Figure 212 show^s a view of a duplex power pump. 
Power pumps are also driven by electric motors. Such 
a pump is illustrated in Figure 213 which is a view of 
the Smith Vaile power pump. 

The elastic attribute of steam available to withstand 
sudden vibrations and jars in the case of direct acting 
steam pumps cannot be taken advantage of by power 
pumps. The problem of providing for the strains, there- 
fore, is a serious one, and necessitates a heavier machine. 

A sinking pump is a pump used for pumping the water 
out of excavations, mines, coffer dams, etc., and the duty 
is generally very hard, as the water to be pumped is 
usually muddy and full of grit. 

Therefore a pump in which the water does not come 
in contact with a water piston, or the interior of a bored 
out water cylinder, and yet will raise the water, would 
seem to be the kind of pump required in this service. 
The Emerson steam pump, made by the Emerson Pump 



528 



ENGINEERING 



Co. of Alexandria, Va., is built along these lines and 
consists of two simple hollow chambers with inlet and 
outlet valves for water. A plain circular slide valve for 
admitting steam alternately to each chamber. A small 
three cylinder engine for actuating this valve. A small 
condenser nozzle at the middle of each chamber, con- 
nected by pipes to the bottom of the opposite chamber 
and two small air check valves at the top of each cham- 
ber. The water is forced from the chamber to a height 
corresponding with the boiler pressure available, by the 
direct pressure of steam, then the steam is condensed to 




FIGURE 208. 



SECTIONAL VIEW BUFFALO DUPLEX PISTON PATTERTQ 
PUMP. 



form a vacuum and cause the chamber to fill again ; one 
chamber fills while the other is discharging. 

Figure 215 shows a sectional view of this pump and 
the following description will serve to make its construc- 
tion plain : 

It consists in common of two vertical chambers B and 
C cast together at the bottom end; each chamber hav- 
ing suction valves L at the bottom, opening upward from 
the common chamber into which the suction pipe A en- 



PUMPS 



529 



ters ; and discharge valves R opening upward into the 
common chamber from which the discharge or deHvery 




pipe U extends. The seats for these valves are of gun 
metal bronze, and very heavy and substantial. They are 



530 ENGINEERING 

held in position by heavy bolts, which are screwed in 
from the outside, and copper w^ashers under their heads 
to prevent their leaking. The valve stems are also of 
gun metal bronze and very heavy. The valves are of 
medium hard rubber. The openings through the seats 
are large and the combined areas of the valve openings 
largely exceed the areas of the suction and discharge 
pipes with which they connect, the design being such as 
to admit of large openings with a small lift or movement 
of the valve. The valves L and R are easy of access 
through openings which are closed by substantial cover 
plates w^hich are shown at D.D. On the top end of each 
chamber is a flange, having cast to its lower or inside 
face a baffle plate G, located opposite the steam port 
which enters through this flange. The purpose of this 
baffle plate is to distribute the steam evenly and prevent 
it from agitating the surface of the water in the cham- 
bers. The top side of this flange has a ground ball joint 
to which the main steam chest connects. The condenser 
nozzles F are of gun metal bronze, and are screwed firmly 
into the walls of each chamber from the outside, and are 
each connected with the bottom of the opposite chamber 
by an extra heavy pipe into which is a check valve open- 
ing upw^ard. As the pressure in the chambers alternates, 
sufficient water will be injected through nozzles F into 
the opposite chamber for condensing the steam therein 
and forming a vacuum promptly. A small air check 
valve P, opening inwardly, attached to each chamber at 
the top end, admits a small quantity of air while the 
chamber is filling, which cushions the ram action of the 
water, prevents shocks, fills the clearance space at the 
top with air under pressure and places a stratum of air be- 
tween the steam and water, effectively preventing con- 



PUMPS 



531 




532 



ENGINEERING 



densation. The specific gravity of air being greater than 
that of steam, the air pocket remains below the steam and 
prevents its contact with the water; forms an elastic 




cushion which receives the excess of inflow without noise 
or shock, and gives it out again silently at each impulse. 
From the steam chest there is a port leading to each 



PUMPS 533 

chamber. Steam is admitted to, and cut off from them 
alternately, by a flat rotary slide valve which is located 
within the steam chest, and so designed that when steam 
is being admitted to one chamber it is cut off from the 
other. One chamber is filled while the other is discharg- 
ing. The motion of this valve is continuous and slow. 
Both chambers fill and empty while the valve is making 
one revolution. This valve is driven by a small three 
cylinder engine E Figure 215 which is rigidly attached 
to the under side of the steam chest. The engine crank 
«haft extends into the steam chest in the center of the 
bearing around which the valve rotates, and a positive 
geared connection is made between the engine and valve, 
by cut gears of steel and bronze, so arranged that the 
engine runs faster than the valve. 

Steam is admitted into the central chamber of the 
engine through a small pipe that connects with the main 
steam supply pipe, as shown, and presses alike on the 
inner side of the three pistons, but a small circular slide 
valve which is driven by the end of the crank pin, opens 
ports which connects with the outer end of one piston, 
throwing that piston into equilibrium, but the three pis- 
tons collectively out of equilibrium, causing a rotary mo- 
tion of the crank shaft and slide valve. The motion of 
the engine is controlled by a small globe valve N in its 
exhaust pipe just below the engine, after leaving which 
the exhaust pipe passes down between the chambers and 
into the common suction chamber where the exhaust 
steam from the engine is condensed. There is also a 
branch valve in the exhaust pipe of the engine opening 
outside, which can be used for controlling the motion 
of the engine instead of the one just named, if desired. 
Above the main steam chest S is a globe valve O io\' 



534 



ENGINEERING 



regulating the amount of steam that enters the pump 
to suit conditions. 

Lugs H are cast into each chamber for suspending 
the pump when it is necessary. When it is desirable to 
set the pump on a foundation a base is furnished with it. 

In the type of pump shown in Fig. 217 a hard iron 




FIGURE 212. DUPLEX POWER PUMP. 



plunger moves in two working-barrels havnig stuffing 
boxes and glands fitted with swing bolts for convenience 
in packing. The valves are of medium hard rubber, with 
brass seats, bolts and springs, the valve chamber being 



PUMPS 



535 




536 



ENGINEERING 



independent and easily removable for inspection or re- 
pairs. The suction valve chamber is fitted with auto- 
matic air valves for relieving the pump of air, and the 
discharge air chamber has a cock for the same purpose. 
The discharge elbow is fitted with a standard flange and 
has a cock for drawing ofif the water in discharge pipe 




FIGURE 214. DEAN SINGLE CYLINDER POWER PUMP. 



when desired. The bottom flange of the lower working 
barrel has swing bolts for convenience of removal in order 
to take out sand or gravel, and the discharge air cham- 
ber is in one piece, securing compactness and minimum 
weight. 

The steam cylinder has a recently improved valve 



PUMPS 537 

gear, without external moving parts, thus reducing the 
Uability to injury from accident or rough usage. 

The combined Automatic Receiver and Feed Pump il- 
lustrated in Fig. 218 is designed primarily to drain heat- 
ing systems and automatically deliver to the boilers the 
water of condensation in its hottest condition. It is, 
therefore, a necessary and economical apparatus for office 
buildings, hotels, apartment houses, factories, etc. It is 
also a valuable auxiliary in connection with oil refineries, 
brick yards, chemical laboratories, etc. 

Its operation is entirely automatic, being placed in a 
position to receive by gravity the condensed water from 
the entire system for which it is operating, and as the 
returns accumulate in the receiver, the float located there- 
in gradually rises and opens a special valve, admitting 
live steam to the steam chest of pump. As soon as the 
receiver is relieved of its condensed water, the pump 
stops and does not resume action until water again ac- 
cumulates. 

Both receiver and pump are mounted on a cast iron 
base, the height of receiver being restricted so that it 
affords a drain for the lowest pipe or radiator. 

Should the pump be desired as the sole means of feed- 
ing the boilers, a sufficient quantity of cold water may be 
introduced directly into the receiver to supply the de- 
ficiency occasioned by leakage, etc. 

It will be observed, therefore, that this apparatus is 
desirable and economical in the highest degree, not only 
on account of the direct saving effected, but it relieves 
the system of ever accumulating condensation, returning 
it directly to the boilers at a temperature closely ap- 
proximating the boiling point, and also relieves the radia- 
tors, coils, etc., of that objectionable hammer due to the 
presence of entrained water. 



638 



ENGINEERING 




FIGUEE 215. SECTIONAL VIEWS OF THE EMERSON STEAM PUMP. 



?IJ> 



£3^; 






^MC 






&^~'-^'"'^'l< 






PUMPS 



539 



riGUBE 216. 



FRONT AND REAR VIEWS OF THE EMERSON STEAM 
PUMP. 



540 ENGINEERING 



QUESTIONS. 

1. What is a pump? 

2. What is a necessary part of a pump? 

3. What is the seat of a valve ? 

4. Describe three different types of valves. 

5. What kind of material is generally used in making 
pump valves? 

6. Describe the double beat valve. 

7. Describe in general terms the most simple form of 
pump. 

8. How much pressure per square inch does the at- 
mosphere exert upon all surfaces that come in contact 
with it? 

9. Give the weight of a cubic foot of water at a tem- 
perature of 39°. 

10. What is the height of a column of water balanced 
by the atmosphere ? 

11. Suppose a pump piston is at the end of the stroke 
and it starts and moves towards the other end, what 
.occurs behind it? 

12. Then when a vacuum is created behind the pump 
piston what effect does the atmospheric pressure have 
upon the water? 

13. When the pump piston starts on the return 
stroke, what becomes of the water ? 

14. If the suction pipe is air tight, and the pump in 
good condition how high may the water be lifted by 
suction? 



PUMPS 



S^ 




riGUBE 217. THE CAMERON MINE SINKING PUMPW 



542 



ENGINEERING 



15. In pumping water, what unavoidable drawbacks 
are there to overcome ? 

16. Describe the operation of a double acting pump. 

17. How high should the valves of a pump lift, in 
order to perform efficient service? 

18. How high should a hinged valve rise? 




FIGURE 218. AUTOMATIC PUMP AND RECEIVER. 



19. How are the water pistons of pumps usually ac- 
tuated in steam plants? 

20. What is one of the leading features of the Cam- 
eron steam pump? 

21. How are the water valves arranged? 

22. What kind of a valve gear has the Dean steam 
pump ? 



PUMPS 543 

23. Describe briefly a duplex steam pump. 

24. What type of steam valves do the Buffalo, 
Worthington and many other duplex pumps have? 

25. What kind of a steam valve has the Epping Car- 
penter steam pump ? 

26. What is a power pump? 

2y. What is a sinking pump, and for what purpose 
is it used? 

28. Describe briefly the construction of the Emerson 
sinking pump. 

29. Has this pump a water piston? 

30. Then how is a vacuum created in the water 
chamber ? 

31. Describe the construction of the Cameron sinking 
pump. 

32. Describe the construction and operation of an 
automatic receiver and feed pump? 



j;44 



ENGINEERING 



SETTING THE STEAM VALVES OF DUPLEX 
PUMPS. 

The duplex steam pump consists of two steam pumps 
placed side by side, and so combined that one piston acts 
to give steam to the other, after which it finishes its own 
stroke and waits for its steam valve to be acted upon by 
the other piston before it can start on the return stroke. 

This slight pause of the pistons at each end of the 
stroke allows the water valves to seat quietly, thus pre- 
venting any shock or jar. 




Valve-operating gear— Duplex steam pump. 

In setting the steam valves the pistons are so placed 
relatively to each other, that when one is at mid stroke, 
the other one is just about to finish its stroke. This 
arrangement effectually prevents there being a dead 
point, because one or the other of the steam valves is 
always open. 

These valves are always adjusted by the builders be- 
fore the pumps are sent from the shops, but if owing to 
a breakdown, it should become necessary to re-set the- 
steam valves the following rules should be observed. 



SETTING STEAM VALVES 546 

Place one of the pistons at mid stroke. This may be 
accomplished by removing the cyhnder head, and then 
by means of a small jack placed against the piston move 
it gradually along until the rocker arm connected to the 
piston rod stands vertical as shown by a plumb bob. 

Then place the other piston at four-fifths of the com- 
pletion of its stroke. The steam valves, v^hich with 
this type of pumps have no lap should then be adjusted 
in such manner that the one for the piston at mid stroke 
just covers both the steam ports, while that one for the 
piston at four-fifths stroke should be in such a position 
that, being acted upon by the motion of the opposite 
piston through the medium of the rocker arms it will 
have a slight lead when its piston has finished its stroke. 

QUESTIONS. 

1. Describe the construction of a duplex steam pump. 

2. How are the steam valves of this type of pump 
actuated ? 

3. How are the pistons placed relatively to each 
ether? 

4. Is there a dead point in the strokes of the pistons ? 

5. Have the steam valves lap? 

6. Describe the process of adjusting the steam valves. 



CHAPTER XIII. 
LUBRICATION 

Next to the all important problems of keeping the 
water in the boilers at the proper level, and maintaining 
a sufficient supply of steam, comes the proper lubrication 
of the bearings, and other rubbing surfaces on the en- 
gine. If these are not oiled as they should be, the 
efficiency of the engine will be reduced, and besides there 
is a constant danger of some one of the heavy bearings 
becoming heated, and most likely cause a shut-down. 

In discussing the problem of lubrication it is well to 
first study the laws of friction of plane surfaces in con- 
tact. 

There are five of these laws which are commonly 
accepted relative to this subject. 

Friction is the resistance caused by the motion of a 
body when in contact with another body that does not 
partake of its motion, and the laws that control this re- 
sistance are as follows : 

First — Friction wnll vary in proportion to the pressure 
on the surfaces, that is if the pressure increases, the fric- 
tion will be increased and vice versa. 

Second- — Friction is independent of the areas of the 
surfaces in contact, but if the pressure or friction be 
distributed over a larger area, the liability of heating 
and abrasion becomes less than it would be if the friction 
is concentrated on a smaller area. 

Third — Friction increases with the roughness of the 
surfaces, and decreases as the surfaces become smoother. 

546 



LUBRICATION 547 

Fourth — Friction is greatest at the beginning of mo- 
tion. Greater force is required to overcome the friction 
at the instant of starting tO' move a body, than is required 
after motion has commenced. 

Fifth — Friction is greater between soft bodies than it 
is between hard bodies. 

These five laws were formulated in the years 1831-33 
by Gen. Arthur Morin, a French engineer, who made 
many experiments relating to the friction of plane sur- 
faces in contact, but numerous experiments in later 
years by many eminent engineers have demonstrated 
that these laws are not altogether rigid, and that they 
can only be accepted in so far as they relate to the 
friction of dry surfaces in contact, or lubricated surfaces 
moving under light pressures, and at slow speed. As 
friction is always a resisting, and retarding factor, its 
tendency is to bring everything in motion to a state of 
rest. With machinery in motion the friction between 
the surfaces of the parts moving in contact tends to 
cause them to adhere to each other. 

Therefore in order to successfully and economically 
operate the machinery, it is absolutely necessary that a 
lubricant be used that will distribute itself over these 
surfaces, and thus prevent them from coming in direct 
contact with each other. 

Friction, however, is useful in many ways, as for in- 
stance, the friction of the belt in contact with the rim 
of the pulley causes power to be transmitted from the 
engine to the machines throughout the shop. Then also 
the friction or adhesion of the driving wheels of the loco- 
motive makes it possible for the engine to start a heavy 
train and keep it moving. 

The friction of the brake shoes on the car wheels 



648 



ENGINEERING 



makes it possible to stop a train in much less time than 
if it were allowed to stop of its own accord. 

There are two kinds of friction in mechanics, viz., the 
friction of solids, and the friction of liquids. It is the 
friction of solids that the engineer has to deal with 
mainl\% and this kind of friction for convenience may 
be again divided into two classes, viz., rolling friction, as 
for instance a journal revolving in its bearings, or a 
crank pin in its brasses, and second, sliding friction, as 




FIGURE 219. 



the cross head on the guides, or the piston travelling 
back and forth in the C3dinder. 



CO-EFFICIENT OF FRICTION. 

By this term is meant the relation that the power re- 
quired to move a body, bears to the weight or pressure 
on that body. 

This definition may be expressed in another, and per- 
haps plainer form, as follows : 

The co-efficient of friction is the ratio between the 
resistance to motion, and the perpendicular pressure, and 
is determined by dividing the amount of the former by 



LUBRICATION 64^ 

the latter. Figures 219 and 220 will serve to illustrate in a 
graphic manner the second law of friction and also ex- 
plain one method of determining the co-efficient of fric- 
tion. 

A block of iron or other metal is drawn across the 
surface of the table top by means of weights suspended 
from a cord attached to one end of the block, and pass- 
ing over a small pulley or roller at one end of the 
table. The block has a flat surface on one side, while on 
the opposite side there are four small projections or legs, 
one on each corner, and each leg has a sectional area of 
one square inch. The size of the block may be assumed 
to be 8 inches wide, 12 inches long and 2 inches thick, 
and its weight may be taken at 50 pounds. In Figure 219 
the block is placed upon the table with its flat or largest 
bearing surface down. This surface has an area of 
8 inches by 12 inches=96 square inches in contact with 
the surface of the table, and it is found that by placing 
weights on the cord until the block begins to move, and 
keep moving requires a weight of 7 pounds. Now it 
might be supposed that if the block were reversed so 
that it would rest on its four legs it could be moved 
across the table with much less weight on the cord than 
was required in the position shown in Figure 219, but 
such is not the case, as shown by Figure 220 and which 
can also be mathematically demonstrated. 

In the experiment illustrated in Figure 219 the co-effi- 
fient of friction is resistance 7 pounds divided by weight 
or pressure 50 pounds=.i4; that is it requires a force of 
.14 pounds to move one pound of weight. The pressure 
per square inch of area=weight 50 pounds divided by 
area 96 square inches=.52 pounds. The co-efficient be- 
ing .14 pounds, the pull per square inch of surface re- 
quired to move the block is .52X.i4=-0729 pounds, which 



550 



ENGINEERING 



multiplied by the total area 96 square inches equals 
6.9888 or practically 7 pounds. Referring to Figure 220 
where the block is reversed, and stands on four legs, 
each leg having an area of one square inch in contact 
vv^ith the surface of the table, the total contact is four 
square inches, but the pressure remains the same, viz., 50 
pounds. Therefore the pressure per square inch of 
area=50-f-4=i2.5 pounds, which when multiplied by the 
co-efficient .14 equals 1.75, w^hich is the pull per square 
inch of surface, and there being 4 square inches, the total 




FIGURE 220. 



pull=i. 75X4=7 pounds. It will thus be seen that the 
extent of surface in contact does not affect the friction 
so long as the weight or pressure remains constant, but 
by allowing the larger area of surface to come into con- 
tact with the table surface thus distributing the pressure 
over a greater area, reduces the liability of heating and 
abrasion because the pressure per square inch is so 
much less. 

In machine design, especially engine bearings, and 
crank pins, the object should be to obtain as large a 
surface as possible in order that the pressure per square 



LUBRICATION 



551 



inch may be reduced. By making the bearings of proper 
proportions, by using bearing metals having the greatest 
anti-friction value, by keeping the shafting in line, and 
by the use of the best and most suitable lubricants, and 
lubricating devices, or by using self-oiling bearings 




FIGURE 221. 



v^herever possible, the friction losses may be reduced to 
a very small percentage of the total power developed by 
the engine. Modern engine construction, and methods of 
lubrication have in recent years been brought to such 
a degree of mechanical refinement that the friction loss 
per horse power is only 2 or 3 per cent. This low per 
cent of friction loss has been brought about in the case 
of high speed engines by properly proportioning, and 
balancing the rotating parts, and by the use of lubricat- 



652 



ENGINEERING 



ing apparatus that keeps the bearing continuously flooded 
in a bath of oil. 

Great care should be exercised by the engineer in the 
selection of piston rod, and valve stem packing, and in 
its application and adjustment, as otherwise there will 
be considerable friction loss, especially if the packing is 
unsuitable or becomes hard from too long service, or has 
been screwed up too tightly. 

Prof. Chas. H. Benjamin, in a paper presented at the 
meeting of the A. S. M. E. December, 1900, gives the re- 
sults of a series of tests made by himself, at the Case 
School of Applied Science, in Cleveland, Ohio, to deter- 
mine the amount of friction caused by various kinds of 
piston packing. Figure 221 shows the device used by 
Prof. Benjamin in making the tests. 

Figure 222 is a sectional view of the same machine, 




FIGURE 222. 



which consisted of a cast iron cyUnder 6x12 inches, 
fitted at each end with a suitable head, and stuffing box 
and gland arranged for a two-inch piston rod. The 
rod was given a reciprocating motion, through the 
medium of a slotted cross head, and crank, and a pulley 
on the crank shaft was connected by a belt to a dynamom- 
eter. Steam was admitted to the cylinder through the 
pipe shown in Figure 221 and the water condensation 
was drawn off at the bottom, while a steam gauge showed 



LUBRICATION 553 

the pressure in the cyHnder. The gland nuts were us- 
ually tightened with the fingers only, but when a wrench 
was used, a spring balance was attached, and the turn- 
ing moment was noted. The stroke of the rod was 4.25 
inches, and the revolutions were 200 per minute, giving a 
piston speed of 141 feet per minute. Seventeen different 
kinds of packing were used, the materials of which were 
rubber, cotton, asbestos, hemp, lead, and flax. 

Some of these packings were combined with mica, 
graphite, and paraffine. The various packings were 
fitted according to the directions of the makers, and the 
routine of the tests as they were conducted was as 
follows : 

The machine was first run without packing, in order 
to determine the friction of the empty apparatus. The 
packing was then inserted, and steam turned on, the 
gland nuts being tightened just sufficient to prevent leak- 
age, and the packing was then tested under various pres- 
sures, each test lasting from 15 to 40 minutes. The gland 
nuts were then tightened with the wrench, and spring 
balance to various pressures, and other sets of read- 
ings taken, after which cylinder oil was applied to the 
rod, and the difference in friction noted. These tests 
were measured by means of a Flather recording dyna- 
mometer, and a Weber box gear dynamometer, the read- 
ings being taken at short intervals and averaged. The 
results of these tests are summed up in tables 20 and 21. 
Table 20 gives a summary of the results, showing the 
average horse-power absorbed by each packing at various 
pressures, and for purpose of comparison, the power at 
50 pounds of steam pressure. Table 21 shows the in- 
creased friction caused by tightening the gland nuts, and 
also the beneficial effect of oiling the rod. The different 
packings are numbered. 



554 



ENGINEERING 



The general conclusions arrived at from this series of 
tests are as follows : 

First — That the softer rubber, and graphite packings 
absorb less power in friction than the harder kinds do. 

Table 20. 



Kind of 
Packing. 


No. of 

Trials. 


Total 
Time of 
Run in 
Minutes. 


1 


5 


22 


2 


8 


40 


8 


5 


25 


4 


5 


25 


5 


5 


25 


6 


5 


25 


7 


5 


25 


8 


5 


25 


9 


3 


15 


10 


3 




11 


5 


25 


12 


5 


25 


13 


5 


25 


14 


5 


25 


15 


5 


25 


16 


5 


25 


17 


5 


25 



Average 

H. P. 

Con- 
sumed by 

Each 

Box. 



H. P. 

Con- 
sumed at 

50 lbs. 
Pressure 



.091 
.049 

.037 
.159 
.095 

.368 
.067 

.082 

.200 

.275 
.157 
.266 
.162 

.176 

.233 

.292 

.128 



.085 
.048 

.036 
.176 
.081 

.400 
.067 

.082 

.182 

.172 
.330 
.230 

.276 

,255 

.210 

.084 



Remarks on Leakage, etc. 



Moderate leakage. 
Easily adjusted; 

slight leakage. 
Considerable leakage. 
Leaked badly. 
Oiling necessary; 

leaked badly. 
Moderate leakage. 
Easily adjusted and 

no leakage. 
Very satisfactory; 

slight leakage. 
Moderate leakage. 
Excessive leakage. 
Moderate leakage. 
Moderate leakage. 
No leakage; oiling 

necessary. 
Moderate leakage; 

oiling necessary. 
Difficult to adjust; no 

leakage. 
Oiling necessary; no 

leakage. 
No leakage. 



Second — That oiling the piston rod will reduce the 
friction of any kind of packing. 

Third — That there is almost no limit to the friction 



LUBRICATION 



555 



loss that can be caused by the injudicious use of the 
wrench. 

Variations of friction of hibricated surfaces occur with 
every change of condition of either the bearing or journal 
surfaces, or of the lubricant applied to them. The condi- 
tions that produce the greatest differences in ordinary 
lubrication are, the nature and quality of the lubricant, 

Table 21. 



Kind of 
Packing. 


Horse-power Consumed by Each Box, when 

Pressure was Applied to Gland Nuts by 

a Seven-inch Wrench. 


H. P. Before and 
After Oiling Rod. 




5 Lbs. 


8 Lbs. 


10 Lbs. 


12 Lbs. 


14 Lbs. 


16 Lbs. 


Dry. 


Oiled. 


1 


.120 




.136 






.390 


.055 
.154 

.323 
.067 
.533 
.666 
.454 
.454 




3 




.021 


4 




.248 
.220 
.348 
.126 
.363 
.666 
.405 
.161 
.317 
.526 
.327 
.198 




.303 




.123 


5 




.430 

.228 
.500 






6 




.194 


7 




.260 
.535 


.330 
.520 


.340 
.533 


,053 


8 




.236 


9 




.636 


11 




.454 
.242 
.394 

.860 

.277 








.176 


12 




.359 

.582 

.380 


.454 




.122 


13 








15 






16 






17 













the nature and condition of the wearing surfaces, and 
the speed, pressure, and temperature. 

LUBRICATING OILS. 

The engineer in charge of a plant will always find on 
the market a wide range of petroleum products to choose 
from to meet the various conditions that will show up in 



556 ENGINEERING 

the proper lubrication of the machinery under nis charge. 
The ordinary faciHties of the engine room do not usually 
afiFord means to make elaborate tests of oils, and other 
lubricants, but an engineer can make valuable compara- 
tive tests of different grades of oil on his engine, or other 
machinery. 

For instance by means of a thermometer placed in the 
bearing, with the bulb resting on the shaft, or immersed 
in the oil chamber, the temperature of the bearing may 
be noted, while it is being lubricated with various grades 
of oils, and their qualities thus determined. Of course 
in tests of this kind, care should be taken that the rate 
of oil feed, the belt tension, the pressure on the bearings, 
and the speed remain as near constant as possible, and 
an allowance should also be made for any difference in 
the temperature of the room during the tests. A good 
and efficient lubricant should possess the following char- 
acteristics : 

First, sufficient ''body" to keep the surfaces apart, but 
the greatest possible fluidity consistent with this. 

Second, a minimum coefficient of "internar' friction 
in actual service. 

Third, must not dry or ''gum" and must not contain 
free acids or other corrosive ingredients. 

Fourth, must not be readily thinned, vaporized or ig- 
.lited by heat or stiffened by the cold encountered in the 
service to be performed. 

Fifth, must be absolutely free from all gritty foreign 
substances. 

Sixth, it must be especially adapted to the conditions 
for which it is chosen. 

Experience has proved that in lubrication the best is 
nearly always the cheapest in the end and that the con- 
sumer can better afford to use the highest priced lubri- 



LUBRICATION 557 

cants the market affords than accept those of lower value 
as a gift. 

The cost of lubrication is not merely the market price 
of lubricants but their cost plus the cost of the friction 
accompanying their use. The value, not the cost, of the 
lubricant, is the point worthy of greatest consideration. 
What it will do, not what it costs per pound or per gal- 
lon. No greater error can be made than to economize upon 
the quality of lubricants, for even under the most ex- 
travagant conditions the cost of lubricants represents but 
a very small fraction of the cost of fuel and repairs and 
depreciation of poorly lubricated engines and machinery. 
The best lubricant for a bearing under normal condi- 
tions may not do so well after heating commences, a 
thick viscous oil which under ordinary conditions on 
high speed machinery would be comparatively wasteful 
of power is often an excellent lubricant for a hot bearing, 
and for the following reason : an engineer on finding a 
bearing heating up will apply the ordinary oil freely and 
at the same time loosen up the bolts so as to allow for 
increased expansion and free flow of oil ; if the heating 
continues, and the engine or machinery must be kept 
in operation at all hazards, he will turn to his cylinder 
oil, apply it freely, and often with good results. The 
reason of this is that the cylinder oil, owing to its high 
fire test (from 550 to 600) became thin and limpid with- 
out burning, and flowed freely between the close-fitting 
surfaces and kept them apart, and at the same time, 
absorbed the heat that would otherwise have gone into 
the metal and carried it away, while the engine oil, being 
of lower flash test, vaporized, and if the bearing got hot- 
enough, caught fire. 

In man}' cases the use of pure graphite or plumbago, as 



558 ENGINEERING 

it is sometimes called, will prove to be beneficial especially 
on heavy bearings that are inclined to heat. 

The essential function of graphite is that of an auxil- 
iary or accessory lubricant, with which to perfect and 
maintain the working surfaces in a condition of high 
polish and great smoothness, so that the oils and greases 
used as the actual lubricating film may the more success- 
fully perform their particular service. They have only 
to separate two highly-polished and perfectly fitted sur- 
faces and to reduce friction to the lowest possible point. 

Graphite allows the safe and satisfactory use of less oil 
or grease than would otherwise be necessary because 
there is far less actual wearing out of the oil between 
the smooth surfaces. 

Inasmuch as metallic wear is nearly eliminated, the oil 
does not become rapidly charged with fine metal particles 
and lose its lubricating value. 

Thinner lubricants can generally be used. Graphite 
increases the endurance and efficiency of oil and grease 
lubricants because it relieves them of a very great part 
of the duty they otherwise have to perform. 

Whether graphite is fed at regular intervals or only 
occasionally the results are much the same, inasmuch as 
the coating of graphite persists for a considerable period 
after application. 

In 1902 Professor W. F. M. Goss of Purdue Uni- 
versity conducted a long series of tests to determine the 
value of Dixon's Flake Graphite as a general lubricant 
for bearings, and as applied to railroad air brake equip- 
ment. 

The tests extended over a period of many months and 
were made, not to create arguments in favor of Dixon's 
Graphite but to enlarge the sum of information on the 
subject of graphite lubrication. 



LUBRICATION 559 

The following extracts are taken from the report : 

"From the earlier and rather limited uses of graphite 
in lubrication, the field has gradually widened to include 
its use with light oils, with water, and, in some cases, 
unmixed with other materials. It is no longer regarded 
merely as a material for an emergency, but now has a 
place in the ordinary and usual routine of the engineer's 
day. ... 

'The demand for graphite has come because men 
charged with the responsibility of keeping machinery 
moving have found it beneficial in their work, and not 
because manufacturers and plant owners pressed its use 
upon them. 

''It is not to be presumed that because a material is sold 
as graphite it will give good results in lubrication ; it 
must be free from grit and other impurities and properly 
graded for the work. . . . 

"Graphite does not behave like oil, but associates itself 
with one or the other of the rubbing surfaces. It is 
worked into every crack and pore in the surfaces and 
fills them, and if the surfaces are ill-shaped or irregu- 
larly worn, the graphite fills in and overlays until a new 
surface or more regular outline is produced. When ap- 
plied to a well fitted journal the rubbing surfaces are 
coated with a layer so thin as to appear hardly more 
than a slight discoloration. If, on the other hand, the 
parts are poorly fitted, a veneering of graphite of vary- 
ing thickness, which in the case of a certain experiment 
was found as great as 1-16 inch, will result. The char- 
acter of this veneering is always the same, dense in 
structure, capable of resisting enormous pressure, contin- 
uous in service without apparent pore or crack, and pre- 
senting a superficial finish that is wonderfully smooth 
and delicate to the touch.'' 



560 ENGINEERING 

In the lubrication of the interior wearing surfaces of 
the valves and cylinders of steam engines conditions will 
be met which are altogether different from those en- 
countered in the lubrication of bearings and journals. 

In the latter case, the working and comparing of one 
oil with another, and the results obtained can be easily 
determined by noting the changes of temperature, etc., 
but in internal lubrication the conditions are altogether 
different. 

In the case of journals and bearings, the oil can be 
applied directly to the surface to be lubricated; in cylin- 
der lubrication one must depend upon the flow of steam 
to convey the oil to the parts or wearing surfaces re- 
quiring lubrication. 

The points that govern the conditions of interior lubri- 
cation are : The conditions of the surfaces, the steam 
pressure, the amount of moisture in the steam, the piston 
speed, weight and fit of the moving parts, and the make 
or type of the engine. 

An automatic cut-off engine with balanced or piston 
valves will usually require less oil than an engine with 
a heavy unbalanced valve. 

A large cylinder whose piston is supported by a ''tail- 
rod" is more easily lubricated than one whose heavy 
piston drags back and forth over the bottom of the 
cylinder. 

An oil to be used as a cylinder lubricant in order to 
give good results must possess certain essential prop- 
erties. 

It must be of high flash test, so that it will not volatilize 
or vaporize when in contact with the hot steam; it must 
have good viscosity or body when in contact with the hot 
surfaces, and should adhere to, and form a coating of oil 



LUBRICATION 561 

SO as to prevent wear and reduce as much as possible the 
friction of the moving parts. 

While the quality of a cylinder' oil as shown by the use 
of testing instruments will give one a general idea of 
its lubricating value, the engineer who is studying the 
question of cylinder lubrication can determine more ac- 
curately its exact value by experimenting on his engines 
and pumps and under the conditions peculiar to his own 
plant. 

LUBRICATING APPLIANCES. 

The successful lubrication of an engine depends in a 
large measure upon the character of the appliances that 
are used to convey the lubricant to the wearing surfaces. 

For steam cylinder lubrication the hydrostatic or sight 
feed type of lubricator is in most general use ; this type 
of lubricator depends for its operation upon the displace- 
ment of the oil by a body of water which is formed by 
the condensing of the steam in the condensing chamber 
of the lubricator, the water in passing into the oil cham- 
bers displaces the oil, forcing it up through the sight- 
feed glass, whence it flows through the discharge pipe to 
the cylinder. 

The construction and operation of this class of lubrica- 
tors will be better understood by reference to Figures 
223 and 224. Figure 223 is an exterior view of the well- 
known Detroit sight-feed lubricator, while Figure 224 
is a sectional view showing the interior construction. 
The pipe P shown in Figure 224 connects with a passage 
from the condenser A-2 Figure 223 and when the water 
feed valve A-4 Figure 223 is opened, the water in the 
condenser will pass down the pipe P to the bottom of 
the lubricator, and, being heavier than oil, will stay at 



562 



ENGINEERING 



the bottom, the oil floating above it. The pipe S Figure 
224 leads from the lower sight-feed arm to the upper 
part of the body of the lubricator. The action of the 
lubricator is as follows : 

The body A-i is filled with oil. Steam from the main 
steampipe passes in the connecting pipes above the lubri- 




FIGURE 223. EXTERIOR VIEW DETROIT LUBRICATOE. 



cator, and condenses, filling the condenser A-2 and part 
of the pipe above it with water. The steam also passes 
into the support arm and through the internal tube T into 
the sight-feed glass, where it condenses, filling the glass 
with water. 

As soon as the valve A-4 is opened, the oil in the body 
of the lubricator is subjected to the pressure of the col- 
umn of water extending through the pipe P, the con- 



LUBRICATION 563 

denser and part of the pipe above it, amounting to about 
2 lbs. to the square inch, and in addition to the pressure 
of the steam above the water, amounting- to say lOO lbs. 
to the square inch, or a total pressure of about 102 lbs. 
to the square inch. This we may call the positive pres- 
sure. Liquids communicate pressure equally in all direc- 



FIGURE 224. INTERIOR VIEW DETROIT LUBRICATOR. 

tions, so the oil in the body of the lubricator will press 
in every direction with a force of about 102 lbs. to the 
square inch. It will therefore press down through the 
tube S with this force of 102 lbs. to the square inch. 
Then, if the valve A-7 is opened, a force acting in the 
oppos^'te direction is encountered, which we may call the 



564 ENGINEERING 

back pressure. When the lubricator is connected as 
shown, this back pressure will consist of the column of 
water in the sight-feed glass, and in addition, the steam 
pressure back of this column entering through the sup- 
port arm, and amounting to loo lbs. to the square inch. 
The positive steam pressure being just the same as the 
back steam pressure, these two forces will neutralize each 
other, and we have left, the positive pressure of the 
column of water extending through the pipe P, the con- 
denser and part of the pipe above it, and the back pres- 
sure of the column of water in the sight-feed glass. As 
the latter is much less than the positive pressure, the drop 
of oil is forced through the nozzle. As soon as it leaves 
the nozzle it is no longer acted upon by the positive pres- 
sure, and it rises through the water in the glass from the 
force of gravity, it being lighter than the water. After 
rising through the sight-feed glass it floats through the 
tube T, Figure 224, and through the support arm into the 
main steampipe and goes with the current of steam to the 
steam chest and cylinder. The positive pressure must 
always be greater than the back pressure, or the lubrica- 
tor will not work. For instance, if a lubricator be con- 
nected to a horizontal steampipe by being suspended be- 
low it, the back pressure would be greatly increased, and 
in order to get sufficient positive pressure the condensing 
pipe should rise 18 in. to 24 in. above the horizontal 
steampipe and then descend to the condenser. This will 
give a column of water for positive pressure higher than 
the column of water which acts as back pressure. 



LUBRICATION 565 



TO RE-FILL AND OPERATE. 



Close valves A-4 and A-7. Open drain valve A-8, then 
remove filler plug A-3 and the water will drain out rap- 
idly. When water is all out, close valve A-8, fill with oil, 
and replace filler plug A-3. Then open valve A-4, and 
regulate the flow of oil with valve A-7. The valve A-9 
is to be closed only when desiring to shut ofif steam from 
the lubricator in case of accidental breakage of the glass, 
or when there is danger from freezing. Before starting 
the lubricator, time should be allowed for the sight-feed 
glass and condensing chamber to fill with water from 
condensation. When there is danger from freezing when 
lubricator is not in use, empty the lubricator, and leave 
open valves A-4, A-8 and A-6. Then close valve A-9 
and the small angle valve in condensing pipe above the 
lubricator. 

Figuie 225 shows an external view of the Powell lubri- 
cator ''Class A," for single cylinder engines, and Figures 
226 and 22y show exterior and sectional views of the 
Powell duplex condenser and double up-feed lubricator 
for use on compound and triple expansion engines. In this 
lubricator there may be two or three sight-feeds com- 
bined with one oil chamber. The letters designate the 
different parts, and the operation of this lubricator will 
be easily understood by a study of Figure 227. 

The force feed, or mechanically operated lubricator, 
has come into favor largely within recent years, and it 
certainly has the merit of being positive, while at the 
same time it is not wasteful of oil, being governed by the 
speed of the engine or pump that it is lubricating. This 
type of lubricator is made in single, double, triple, and 
quadruple style, and is operated by attaching the connect- 



566 



ENGINEERING 



ing rod of the oil pump to any movable part of the 
engine that will give it a reciprocating motion. 

Figure 228 shows the Manzel quadruple feed oil pump. 
These pumps are also made with five and six feeds. 
Manzel Brothers Co. also make an agitating force and 




RKUtATING VALVE 



FIGURE 225. POWELL LUBRICATOB. 

A — Oil Reservoir. 

B— Fining Cup. 

C — Valve to Regulate Oil Drops. 

D— Shut-off Valve. 

E — Packing Nuts. 

F — Drain Valve. 

H — Coupling for Condensing Pipe. 

JJ — Sight Feed and Index Glasses. 

K — Plug for Removing and Inserting Glasses. 

M — Condensing Chamber. 

N — Valve to Regulate Water from the Condenser, 

V— Valve to Drain Sight Feed Glass. 

R — Attaching Shank and Valve. 



LUBRICATION 



56; 



sight-feed oil pump for the purpose of feeding graphite 
mixed with the oil. Graphite being a mineral and not 
easily suspended in oil it has always been a rather diffi- 
cult problem to feed it properly along with the oil, but 
the device illustrated in Figure 229 has proved to be very 
successful in feeding the mixture of oil and graphite. 
The action of this appliance will be easily comprehended 




FIGURE 226. POWELL'S DUPLEX CONDENSOR LOCOMOTIVE LUBRICATOR. 



by a reference to Figure 229. The spiral agitating device 
that revolves in the cup is operated by means of the belt- 
drive on the wheel, and bevel gears on the cup. The con- 
struction is simple and durable. Two fillers are used, 
one for oil and one for graphite. No fixed rule can be 
laid down for the amount of graphite to be used, as some 
engines require more than others. Two or three good 
teaspoonfuls to a pint of valve oil, would be a good rule 



568 



ENGINEERING 




FIGURE 227. DESCRIPTION OF INTERNAL PARTS. 



A — Oil Chamber. 

CC — Oil Drop Regulating Valves. 

EE — Brass Protecting Shields. 

F — Drain Valve. 

GG — Removable Plugs to Clean Oil Tubes. 

HH— Packing Nuts. ^ - 

II — Adjustable Rings. 

JJ — Sight Glasses. 

KK — Removable Cages to Replace Glasses. 

MM — Condensers. 

N — Water Valve. 

T — Connecting Coupling to Boiler. 

VV — Cleaning Valves for Sight Glasses. 

W— Water Tube. 

X— Water and Oil Trap. 



LUBRICATION 



569 



to start on, and the engineer can then watch resuks and 
ascertain for himself the proper quantity to use. 

Another rule might be, three teaspoonfuls of graphite 
per day for a 150 horse-power engine. 

INSTRUCTIONS HOW TO ATTACH MANZEL 
OIL PUMPS. 

Place the pump on the frame of an engine or pump 
where it is most convenient to get motion. It can be 




FIGURE 228. MANZEL QUADRUPLE FEED, OIL PUMP* 



bolted to a stud or stand. Attach connecting rod of the 
pump to any movable part that travels back and forth 
such as a valve rod to an engine or rocker arm of a pump. 
(See illustrations on the following pages.) Connect the 
pipe to the pump cylinder. Use % in. pipe for }4 pint 
and pint pumps, and ^ in. pipe for all other sizes ; the 



SsT^Q; " ENGINEERING 

end of pumps and check valves are threaded for these 
sizes, and run to and enter the steam hne or steam chest 
above or below^ the throttle, as desired. Equip the oil 
pipes as near as possible to the steam line with check 
valve; the end marked ''S'' toward the steam line. By 
using a reducer^ ^ in. pipe can be used on the larger size 
pump. 




FIGURE 229. THE MANZEL AGITATING, FORCE AND SIGHT FEED OIL 

PUMP. 

The feed on the "Manzel Improved" Pump is regu- 
lated while in operation on the engine, on the upper 
plungers. To increase the feed screw plunger inward, 
to decrease the feed screw plunger outward, then tighten 
lock-nut. Particular attention is called to the regularity 
of the feed that is obtained on these pumps, under all 



LUBRICATION 



571 



conditions. They can be regulated to feed from nothing 
or one drop to a stream of oil with every stroke of the 
plunger. 

Another good force feed lubricator is the Dietz high 
pressure force feed lubricator made by the Pearl Manu- 
facturing. Co. of Buffalo, New York. This device is 
made either single or double acting, and with from one 
to six feeds. 

Figure 230 shows a double acting three-feed Dietz 




FIGUBE 230. DIETZ HIGH PRESSURE FORCE FEED LUBBICATOB. 



57? 



ENGINEERING 




MANZEL OIL PUMP APPLIED TO CORLISS ENGINE. 




MANZEL OIL PUMP APPLIED TO STEAM PUMP. 



LUBRICATION 



573 



high pressure lubricator, and it is claimed by the manu- 
facturers that it will feed any mixture of oil and graphite 
without becoming clogged, owing to the fact that the 




FIGUBE 231. 



ROCHESTER FORCE FEED LUBRICATOR WITH MONITOR 
SIGHT FEED APPLIANCE. 



valves are of the poppet type, and made of steel, and 
when not opened by the cams, are held to their seats by 
a strong spiral spring in addition to the pressure. This 



574 ENGINEERING 

oil pump IS fitted with a crank, by means of which it 
may be worked by hand, in starting, or should an extra 
amount of oil be required at any time. The pump is 
driven in the usual way by connecting to the valve rod 
of the engine and the feed is regulated by varying the 
^Tavel of the rocker arm. 

Figure 231 shows the Rochester force feed lubricator, 
as it appears with the Monitor sight-feed attachment 
screwed onto the delivery pipe, by means of which the 
engineer is enabled to see the drops of oil as they are 
being fed to the cylinder or bearings. The number and 
size of the drops can be regulated to suit the requirements 
of the engine. 



LUBRICATION 



57? 



QUESTIONS ON LUBRICATION. 

1. What is one of the most important problems con- 
nected with the operation of the engine ? 

2. What is friction ? 

3. What is the first law of friction? 

4. Define the second law of friction. 

5. What is the third law regarding friction? 

6. Give a definition of the fourth law of friction. 

7. Define the fifth law of friction. 

8. When and by whom were these laws first formu- 
lated? 

9. What is the tendency of friction with machinery 
in operation? 

10. How may this friction be largely obviated? 

11. Does friction serve any good purpose? 

12. How many kinds of friction are there in connec- 
tion with machinery in motion? 

13. What is meant by the term coefficient of friction? 

14. What should be the object sought in the design 
of engine bearings ? 

15. What is the friction loss in a correctly designed, 
properly balanced high speed engine, if kept well lubri- 
cated ? 

16. Mention some of the qualities that a good lubri- 
cating oil should possess. 

17. What is the proper kind of oil to use on a bear- 
ing that has started to heat? 

18. Is graphite a good lubricant? 



576 ENGINEERING 

19. What is the essential function of graphite? 

20. Mention some of the points that govern interior 
lubrication. 

21. What properties should a good cylinder oil pos- 
sess? 

?2, Upon what does the successful lubrication of an 
engine depend? 

23. What system of lubrication for cylinders and 
valves is probably most largely used? 

24. What other system is also largely used? 



Eleetncicy for Engineers 

CHAPTER I 

The Electric Current— The Ampere— The Volt— The Ohm^-The 
Watt — Divided Circuits. 

The Electric Current. All electrical phenomena with 
which we have to deal are produced through the 
medium of the electric current. This current flows 
only in a conductor of electricity. Among the most 
noteworthy of the conductors are the various metals; 
the most useful, and in fact the only one in general 
use for light and power purposes, being copper. 

Every conductor offers some resistance to the flow 
of current, just as every pipe offers resistance to the 
flow of steam or water. Just how this resistance varies 
we shall see later on. In order to familiarize ourselves 
with the most important electrical phenomena let us 
consider Fig. i. The current is assumed to leave the 
battery at the +, or positive, pole and flow along the 
wires, etc., to the negative, or — pole, and as it passes 
through the coils of wire wound about the iron bar it 
produces magnetism in the bar. If the bar is of soft 
iron the magnetism lasts only while the current is 
flowing, but a bar of hardened steel will permanently 
retain its magnetism. The current will also heat the 
incandescent lamp until it emits light, and the fine 
wire, R, to the melting point, if desired. In passing 
through the water in the jar, it will decompose it, 
forming oxygen and hydrogen gas. If, instead of 

5 



6 



ELECTRICITY FOR ENGINEERS 



water, the jar is filled with a proper solution, one of 
the copper plates in the solution will be gradually 
eaten away and the other added to. If we now discon- 
nect our wires from the battery and connect I at 2, and 
2 at I, the chemical action in the jar will be reversed, 
the lamp and fine wire, R, will heat as before, no differ- 
ence being noticeable. The iron bar will also be a 
magnet as before, but the end that before attracted 
the north seeking end of a compass needle will now 
reoel it and attract the south seeking end of the same 




FIGURE 1. 



needle, ihe wire which connects the various devices, 
and the devices themselves, constitutes an electric cir- 
cuit, and the current is said to flow in such a circuit 
along the wire, just as water flows in a pipe. The 
solid lines form what is known as a series circuit, 
while the dotted lines form a multiple circuit. T.i the 
latter case, each piece of apparatus receives current 
independent of the others. In the series circuit the 
same current passes through all. If the small wire^ 
is connected to ^, no current will flow through R; it 



ELECTRICITY FOR ENGINEERS 7 

will all flow through a and b. If the wire X be con- 
nected to Y, all current will flow through it and none 
through any other part of the circuit. The current 
obeys the same law as does water; it takes the path 
which offers the least resistance to its flow. 

Such substances as effectually prevent current from 
flowing through them are known as insulators. Some 
of them are 

Dry Air, Mica, 

Glass, Shellac, 

Silk, Oil, 

Asbestos, Paraffine, 

Porcelain, Wool, 

Cotton, Paper, 

Rubber, Gutta Percha, 

and because the following substances have a low resist- 
ance they are known as conductors of electricity. 
Their relative conductivity is in the following order, 
silver being the best: 

Silver, 

Copper, 

Gold, 

Platinum 

Iron, 

Tin, 

Lead, etc. 

The Ampere. The ampere is the unit of volume or rate 
of flow, and in speaking of a flow of so many amperes, 
we mean substantially the same thing, electrically 
speaking, as though we referred to so many gallons of 
water, mechanically speaking. The number of amperes 
flowing over a wire deliver power, much or little, pro- 



8 ELECTRICITY FOR ENGINEERS 

portional to the electromotive force or pressure under 
which they flow; just as the number of gallons of water 
flowing through a pipe toward a water wheel deliver a 
large or small quantity of power to the wheel, propor- 
tional to the pressure under which the water flows. If 
100 amperes were flowing at a pressure of lo volts they 
would produce the same power as though there were 
10 amperes flowing at lOO volts, exactly as lOO gals, of 
water flowing at a pressure of lo lbs. to the square inch 
would produce the same power as lo gals, flowing at a 
pressure of lOO lbs. to the square inch. In both cases, 
however, for convenience, we have not considered the 
size of either wire or pipe, but with the wire, as wnth 
the pipe, as we increase the diameter we decrease the 
friction or resistance. In speaking of the gallon we, 
of course, have something material on which we can 
base the unit gallon. We may take a vessel i ft. wide, 
I ft. long and I ft. high, and this vessel will hold i cu. 
ft. of water. This cubic foot would contain 7% gals.; 
but in the case of the ampere we must adopt another 
method. We shall take an earthenware tank in which 
is contained a solution of copper sulphate and add one- 
tenth of one per cent, sulphuric acid. We shall next 
take two copper plates and hang them into this solu- 
tion, keeping them spaced one inch apart, vertically. 
Having washed these plates in clear water, rounded off 
the corners and dried them thoroughly, we must next 
weigh them very carefully before submerging them in 
the liquid. We may now connect both plates to a 
source from which we can obtain a current of electri- 
city and allow the current to flow from one plate to 
another, through the liquid, for a period of time which 
we must measure by a watch or clock. After current 
has flowed for several hours we will remove the plates, 



ELECTRICITY FOR ENGINEERS 9 

wash them in clean water, and then dip in a bath of 
water containing a very small amount of sulphuric acid 
to prevent oxidization, dry them and carefully weigh 
them again. It will be found that the negative plate 
has increased in weight by what is called electrolytic 
action. Now weigh the negative plate and ascertain 
the exact number of grammes of copper deposited on 
its surface, or, in other words, find how many grammes 
heavier the plate is now than it was before it went into 
the bath. With these data in our possession we will 
multiply the time in seconds that current was passing 
through the plates by .000329 and divide the number 
of grammes deposited on the plate by the result. The 
quotient will be the number of amperes that passed 
from plate to plate. This I give simply to show you 
the manner in which the ampere can be ascertained. 
It is that current which will deposit .000329 gramme 
per second on one of the plates of a voltameter, as 
above described. It is also the current produced by 
one volt acting through a resistance of one ohm. 

In other words, the ampere is that current which 
would be forced over a wire having a resistance of one 
ohm by a pressure of one volt. 

The ampere-hour is the unit of electrical quantity in 
general use. It is the quantity of electricity conveyed 
by one ampere flowing for one hour, or one-half 
ampere flowing for two hours; or again, one-fourth 
ampere flowing for four hours. In each case the sum 
total would be one ampere-hour. It must, however, 
be noted that an ampere-hour with the pressure at no 
volts would deliver just one-half as much power as an 
ampere-hour at 220 volts. 

An ordinary 16 candle-power no volt incandescent 
lamp requires a current of about one-half an ampere. 



10 ELEC^^RICITY FOR ENGINEERS 

while a lamp of the same candle-power at 220 volts 
requires but one-fourth of an ampere, and a 52 volt 
lamp about one ampere. 

A milli-ampere is the one-thousandth (1017) P^^t of 
an ampere. 

The Coulomb. The Coulomb is the unit of quantity. 
It is the quantity of current delivered by one ampere 
flowing for one second. 

The Volt. By electromotive force, volts, or potential, 
we mean electrically about the same as we do when 
speaking of pounds pressure as indicated on a steam 
gauge. If we connect a volt-meter between a positive 
and a negative wire we find that it indicates a certain 
number of volts; the volt-meter then indicates electrical 
pressure just as a steam gauge indicates steam pressure. 
The difference in potential or pressure between two 
wires we will assume to be 100 volts, and the difference 
of potential between the inside of a pipe and the atmos- 
phere also at 100 lbs. to the square inch. The steam 
gauge is closed at one end of the tube which operates it, 
and hence, the pressure from the interior of the pipe 
does not flow into the atmosphere; in other words, the 
resistance offered to the pressure prevents the water 
from escaping into the atmosphere. In the case of 
the volt-meter the resistance of the wires used in its 
construction prevents any great quantity of electricity 
from flowing out of the positive wire and into the 
negative through the volt-meter coil. If the gauge 
were accidentally broken off the pipe, the resistance to 
the pressure on the inside of the pipe would be greatly 
lowered and allow the water to flow into the atmos- 
phere. If a piece of ordinary wire were connected to 
the positive and negative wires, where we have just 
connected our volt-meter, it would form a path of such 



ELECTRICITY FOR ENGINEERS 11 

low resistance and allow all the current to flow through 
it, so there would be no pressure indicated in the volt- 
meter. This would be called a "short circuit/' With 
a vc It-meter there is always a small amount of current 
fiowing from a positive to a negative wire through the 
coil in the meter. This current is neccesary to produce 
the reading on the meter, but we need not consider 
this current at present, the quantity being very small. 

One volt (unit of pressure) will force one ampere 
(unit of current) over one ohm (unit of resistance). 

Potential is a term quite frequently used to express 
the same idea as voltage or electromotive force, but its 
meaning is somewhat different. Suppose that a steam 
engine is working with lOO lbs. of pressure at the 
throttle valve, and exhausting into a heating system or 
system of piping that offers a back pressure of 5 lbs. to 
the square inch; in other words, the resistance to the 
flow of steam out of the exhaust pipes of this engine is 
such that the remaining pressure, when the engine has 
exhausted, is 5 lbs. Now it will readily be seen that 
the total pressure utilized to do the work would be 100 
lbs. less 5 lbs., orgs lbs., and therefore the potential 
would be 95 lbs. Now, if we are using electricity at 
100 volts pressure, and lose 5 volts in overcoming 
resistance, we have a potential of 95 volts left. When- 
ever work is done by a steam engine a certain amount 
of pressure is lost by condensation, doing work and by 
overcoming friction. This loss may be considered the 
same as a loss of potential, for in the use of electricity 
any loss in pressure of volts that may occur from 
doing work or overcoming resistance is called a loss of 
potential. 

In open arc lamps the loss of potential across the 
terminals or binding posts is about 50 volts; that is, 50 



12 ELECTRICITY FOR ENGINEERS 

volts have been absorbed or used In producing light 
You can now readily understand that electromotive 
force means force, pressure, energy, and that by 
potential we mean the capacity to do w^ork or the 
effective pressure to do work. While we are speaking 
of electromotive force we may consider some of the 
advantages of high and low electromotive forces. 
High electromotive force, like steam at high pressure, 
is far more economical in transmission or utilization 
because the quantity may be that much smaller. 

When transmitted to great distances, high electro- 
motive forces, like high water or steam pressures, are 
far more desirable on account of the reduction in fric- 
tion losses; but this is partially offset by the necessity 
of using, in water transmission, a much stronger pipe 
for the high pressure than would be necessary for the 
low pressure, and in the transmission of current at a 
high electromotive force or pressure it becomes neces- 
sary to use wires with far better insulating material 
than would be required for the transmission of elec- 
tricity at low pressure. Increasing the pressure or 
electromotive force always means more danger, even if 
you know the pipes are extra strong or the insulation 
of the wire is of unusually high resistance; for if any- 
thing should happen the consequences would be far 
more serious with high than with low pressures. But 
notwithstanding all this, engineers are continually 
increasing the pressures of electrical machinery. 

Static electricity is a term applied to electricity pro- 
duced by friction, and a static discharge of electricity 
usually consists of an infinitely small quantity but a 
very high electromotive force or pressure. Discharges 
of lightning are extremely high in voltage, but the 
quantity of current that flows is very smalL 



ELECTRICITY FOR ENGINEERS 13 

The Ohm. The ohm is the unit of resistance. Resist- 
ance, electrically speaking, is much the same thing as 
friction in mechanics. If a wire or pipe of a certain 
length is delivering lo gals, or lo amperes at a pressure 
of 100 lbs. or 100 volts, and we propose to double the 
flow without increasing the pressure, it will be necessary 
for us to increase the diameter of the pipe and wire in 
order to lower the resistance of the wire and the friction 
of the pipe to one-half of what it was before. If we 
desire the best results from the pipe, we lower its fric- 
tion by reaming out all burrs and avoiding all unneces- 
sary bends and turns; likewise if we desire the best 
results from the wire we will have the copper of which 
it is constructed as nearly pure as possible, and we 
will install the wire where its temperature will not be 
unnecessarily high, avoiding boiler rooms and other 
hot places. Resistance of the wire increases slightly 
with an increase in temperature. 

For every additional degree centigrade the resistance 
of copper wire increases about 0.4 per cent., or for 
every additional degree Fahrenheit about 0.222 per 
cent Thus a piece of copper wire having a resistance 
of 10 ohms at 32° F. would have a resistance of 11. ic 
ohms at 82° F. An annealed wire is also of lower 
'•esistance than a hard drawn wire of the same size. 
A good idea of the value of an ohm may be had from 
the following table, which gives the length of differ- 
ent wires required to make one ohm resistance. 

FEET PER OHM OF WIRE (B. & S.). 

94 feet of No. 20 605 feet of No. 12 

150 " 18 961 ** 10 

239 " 16 1529 '• 8 

380 •* 14 2432 ** 6 

3867 feet of No. 4 



14 ELECTRICITY FOR ENGINEERS 

We have not as yet established a unit of mechanical 
friction, therefore when we speak of mechanical fric- 
tion we refer to it as requiring a certain quantity of 
power to overcome it. When, however, resistance to 
the flow of electricity is spoken of it is referred to as 
so many ohms. It can be measured in several ways, 
the most reliable and convenient being by an instru- 
ment called the Wheatstone Bridge. It can also be 
calculated if the length and diameter of the wire or 
conductor is known, as will be shown later on. 

The basis of all electrical calculation is Ohm's law. 
This law reads: 

"The strength of a continuous current in a circuit is 
directly proportional to the electromotive force acting 
on that circuit, and inversely proportional to the resist- 
ance of the circuit." In other words, the current is 
equal to the volts divided by the ohms. Expressed in 
symbols, C = E/R; C being current, E voltage, and R 
resistance. If an incandescent lamp having a resist- 
ance of 200 ohms be placed in a socket where the 
pressure is 115 volts, the resulting current through 
such a lamp would be 115 divided by 200, or .575 of an 
ampere. 

From the formula C = E/R, two others are deduced. 
The volts divided by the amperes equal the ohms, 
E/C = R. 

The amperes multiplied by the ohms equal the volts, 
CxR = E. 

The Watt. The watt is the unit of pov^^er. It is an 
ampere multiplied by a volt; just as the unit of mechan- 
ical power, called the foot pound, is the result of the 
pound multiplied by the space in feet through which it 
moves. If a current of say loo amperes, flows over a wire 
at a pressure of 10 volts, the power delivered will equal 



ELECTRICITY FOR ENGINEERS 15 

100 amperes x lo volts = i,ooo watts. If a current of 
10 amperes flows over a wire at a pressure of lOO volts, 
the power would be exactly the same, lo amperes x loo 
volts, or 1,000 watts. But, of course, in the first case it 
would require a wire ten times as large to deliver the 
l,000 watts as would be necessary in the latter case. 
If a weight of lo pounds were being elevated through 
space at the rate of lOO ft. per minute the power 
equivalent would be lo lbs. x lOO ft., or i,000 ft. lbs. 
If an arc lamp consumes lo amperes at a pressure of 
70 volts, its power consumption is lo x 70, or 700 watts. 
One watt is the power developed when 44.25 ft. lbs. 
of work are done per minute. Seven hundred forty- 
six watts equal one horse power. The watt-hour 
is the unit of electric work, and is a term employed to 
indicate the expenditure of one watt for one hour. 
The kilo watt-hour is the term employed to indicate 
the expenditure of an electric power of 1,000 watts for 
one hour. 

The work done per second when a power of one watt 
is being developed is called the joule, and a joule is 
equal to .7375 ft. lbs. 

Electromotive force times current equals watts. 
The square of the current multiplied by the resistance 
equals watts; and the voltage multiplied by itself and 
divided by the resistance equals watts. Expressed in 
symbols, these explanations would look like this: 
W = E X C. W = C X R. W = E^ ^ R. 

First. If we have an electromotive force or voltage o_ 
10 volts and a current of 20 amperes, we have 10 x 20 ~ 
200 watts. 

Second. If we have a current of 10 amperes and a 
resistance of 30 ohms, we would have 10 x 10 x 30 = 3,000 
watts. 



16 ELECTRICITY FOR ENGINEERS 

Third. If we have an electromotive force or voltage 
of 10 volts and a resistance of 20 ohms, we would have 
ID X 10, or 100 -^ 20, or 5 watts. 

In the above formulas E stands for voltage, C for 
current, R for resistance and W for watts. 

Divided Circuits. Currents of electricity, although 
they have no such material existence as water or 
steam, still obey the same general law; that is, they 
flow and act along the lines of least resistance. If a 
pipe extending to the top of a ten story building had 
a very large opening at the first floor, it would be im- 
possible to force water to the top floor. All the water 
would run out at the first floor. If the opening at the 
first floor were small only a part of the water would 
escape through it, some would reach the top of the 
building. The flow of water in each case is inversely 
proportional to the resistance offered to it by the dif- 
erent openings. 

The same thing is true of currents of electricity. 
Where several paths are open to a current of electri- 
city the flow through them will be in proportion to 
their conductivities, which is the inverse ratio of their 
resistances. As an illustration, the current flow 
through all of the lamps, Fig. 2, is the same, because 



FIGURE 2. 

each lamp offers the same resistance. But if we 
arrange a number of lamps as in Fig. 3, the lamps in 
series will offer twice as much resistance as the single 



ELECTRICITY FOR ENGINEERS 



17 



A, 



6b 



FIGURE 3. 



lamps, and will receive but half the current of the: 
single lamp. In Fig. 4 we have still another arrange- 
ment. The lamp A limits the current which can flow 
through B and C, and that current which does flovi 




FIGURE 4. 



divides between B and C in proportion to their con- 
ductivities. If B has a resistance of no ohms and C 
220 ohms, then B will carry two parts of the current 
and C only one. The combined resistance of all 
lamps, Fig. 2, equals the resistance of one lamp 
divided by the number of lamps. The combined resist- 
ance. Fig. 3, equals the sum of the resistances of the 
two lamps at A multiplied by the resistance of B and 
divided by the sum of all the resistances. If the resist- 
ance of each of the lamps were no ohms, the problem 

W^ i. xu 1104-110x110 ^^ T/ 

work out thus: fx^:fnoTTio = 73>^- 

In Fig. 4 the total resistance is \\1^^q + i 10 = 183 >^. 

One practical illustration of the above law may be 

found in the method of switching series arc lamps, 



18 



ELECTRICITY FOR ENGINEERS 



Fig. 5. As long as the switch S is open the arc lamp 
burns, but as soon as the switch is closed the lamp is 




FIGURE 5. 



extinguished because the resistance of the short wire 
and the switch S is so much less than that of the arc 
lamp that practically aii the current flows through S. 



CHAPTER II 

WIRING SYSTEMS — CALCULATION OF WIRES — WIRING 
TABLES. 

Wiring Systems. The system of wiring which is most 
generally used for incandescent lighting and ordinary 
power purposes is called the two wire parallel systetn. 
In this system of wiring the two wires run side by side, 
one of them being the positive and one the negative. 
The lamps, motors and other devices are then con- 
nected from one wire to the other. A constant pressure 
of electricity is maintained between the two wires, and 
the number and size of lamps, or other apparatus, 
connected to these two wires, determine how many 
amperes are required. Each lamp or motor is inde- 
pendent of the others and may be turned on or off 
without disturbing the others. 

A diagram of such a system is shown in Fig. 6. 




FIGURE 6. 

In this system the quantity of current varies in pro- 
portion to the number of devices connected to it. 
Suppose that we are maintaining a pressure or poten- 
tial or electromotive force of no volts on such a sys- 
tem, and that we have connected to the system ten i6 
candle power incandescent lamps, consuming one-half 

19 



20 ELECTRICITY FOR ENGINEERS 

ampere each. The total quantity of current to supply 
these lamps would be 5 amperes. If we should now 
switch on ten more lamps the quantity of current 
would be ID amperes, and the pressure would remain 
no volts. This system is also known as the ''constant 
potential system," or multiple arc system, and among 
the numerous devices used in connection with it are 
the constant potential arc lamp, the shunt motor, the 
compound wound motor, the series motor, incandes- 
cent lamps, etc. Electric street railways are also 
operated on this system. The electricity supplied 
through this system of wiring may be either direct or 
alternating current. 

The series arc system. Fig. 7, is a loop; the greatest 
electrical pressure being at the terminal or terminal ends 




FIGURE /. 



of the loop. The current in such a system of wiring is 
constant, and the pressure varies as the lamps or other 
apparatus are inserted in or cut out of the circuit. 
This system is also called the constant current system. 
The same current passes through all of the lamps, and 
the different lamps are also independent of each other. 

At the present time the series system is used mostly 
for operating high tension series arc lamps. The use 
of motors with it has been almost entirely abandoned. 

The series multiple system, Fig. 8, is simply a num- 
ber of multiple systems placed in series. This method 
of wiring was at one time employed to run incandes- 



ELECTRICITY FOR ENGINEERS 



21 



cent lights from a high tension series arc light circuit, 
but on account of the danger connected with the use 




FIGURE 8. 

of incandescent lamps, operated from a high tension arc 
lamp circuit, the system has been abandoned. It is 
not approved by insurance companies, and conse- 
quently is not often used. 

The multiple series system consists of a number of 
small series circuits, connected in multiple, as shown 
in Fig. 9. This system of wiring is used on constant 




FIGURE 9. 

potential systems, where the voltage is much greater 
than is required by the apparatus to be used, as, for 
instance, connecting eleven miniature lamps, whose 
individual pressure required is 10 volts, into a series, 
and then connecting the extreme ends of such a series 
to a multiple circuit whose pressure is no volts. In 
electric street cars, where the pressure between the 



22 



ELECTRICITY FOR ENGINEERS 



trolley wire and the running rail is 500 volts, it will be 
noticed that the lighting circuits in the car consist of 
five 100 volt lamps in series, and one end of this series 
is connected to the trolley line, the other end being 
grounded on the trucks. 

The three wire system. Fig. 10, is a system of 
multiple series. In this system, as its name implies, 
three wires are used, connected up to the machines in 



^•^ 'A i i A i i 




rA '^ 'i' 9 ^ 9 



FIGURE 10. 



the manner shown in the diagram. Both machines are 
in series when all lights are turned on, but should all 
lights on one side of the neutral or center wire be 
turned off the machine on the other side alone would 
run the other lights. 

One of these wires is positive, the other is negative, 
and the remaining one or center wire is neutral. In 
ordinary practice from positive to negative wire, a 
potential of 220 volts is maintained, while from the 
neutral wire to either of the outside wires a potential 
of no volts exists. The advantages of such a system 
are many, principally among them is the use of double 
the voltage of the two wire system; this reduces the 
current one-half and allows the use of smaller wires. 
This system only requires three wires for the same 
amount of current that would require four in the other 
system. Motors are supplied at 220 volts, while 
lights operate at no. Incandescent lighting circuits 



ELECTRICITY FOR ENGINEERS 2S 

ran be maintained from either outside wire to the 
neutral wire. The saving in copper by dispensing 
with the fourth wire is not the only advantage in the 
saving of conductors. The neutral wire may be much 
smaller than the outside wires because it will seldom 
be called upon to carry much current. 

Inside of buildings, however, where overheating of 
a wire is always dangerous, the neutral wire should be 
of the same size as the others. By tracing out the 
circuits in Fig. lo, it will readily be seen that, so long 
as all lamps are burning, the current passes out of 
dynamo i into the positive wire and from there through 
the lamps (always two in series) to the negative 
or — wire, returning over it to the — pole of dynamo 2, 
So long as an equal number of lamps is burning on 
each side of the neutral, no current passes over the 
neutral wire in either direction. But if the positive 
or + wire should be broken, say at a, dynamo i will no 
longer send current and the lamps between the positive 
and neutral wire will be out. 

Dynamo 2 will now supply the lamps between the 
neutral and the negative wire and for the time being 
the neutral wire will become positive. Should the 
negative wire break at b, the lamps connected to it 
would be out and dynamo i would supply the lights on 
its side, the neutral wire becoming negative. When 
motors of one or more H. P. are used on this system, 
it is usual to connect them to the outside wires using 
220 volts. It is important also to arrange the wiring 
so that an equal number of lights are installed on each 
side of the neutral. When the lights and motors are 
so arranged, the system is said to be * 'balanced." It 
is also very important to arrange so that the neutral 
wire cannot readily be broken. Should the neutral 



24 



ELECTRICITY FOR ENGINEERS 



wire be opened while, for instance, fifty lamps were 
burning on one side and say ten or twenty on the 
other, the ten or twenty would be broken by the excess 
voltage. Grounded wires ordinarily cause more 
trouble than anything else on electric light or power 
circuits, but with the three wire system, the neutral 
wire is often grounded. Grounds on this wire are less 
objectionable than on other wires, because it carries 
very little current, and that current is constantly vary- 
ing in direction, so that no great amount of electrolysis 
can occur at any one place. For full descriptions and 
drawings of methods of wiring, see Wiri?ig Diagrams 
and Descriptions by Horstmann and Tousley, published 
by Frederick J. Drake & Co., Chicago. 

Feeders (see Fig. ii), as the name implies, is a term 
used to designate wires which convey the current to 



Scruicc 




^^v^NNwwwNN nwwsnv ^xN\\\>^^^\^^>\\\^\^^^N^^\\V^ 



5 ^^ .^^;^n:^^<Vx\^\\\^^-^^\^^^^\^^^^^ 



Branch 

Bulldrng, mams 



i Clrcuxts 



In 




FIGURE 11. 



any number of other wires, and the feeders become a 
part of the multiple series, multiple and three wire 
systems. 

Distributing mains are the wires from which the wires 
entering buildings receive their supply. 



ELECTRICITY FOR ENGINEERS 25 

Service wires are the wires that enter the buildings. 

The center of distribution is a term used for that part 
of the wiring system from which a number of branch 
circuits are fed by feeder wires. In most buildings 
the tap lines are all brought to one point, and ter- 
minate in cut-out boxes. These cut-out boxes are 
supplied by the main. Each floor of the building may 
have a cut-out box, or each floor of the building may 
have several cut-out boxes of the above description. 

Calculation of Wires. If we desire to transmit or 
deliver a certain quantity of liquid through a pipe, 
we estimate the size of the pipe and 
the comparison of sizes in the pipes 
by squaring the diameter, in inches, 
and multiplying the result by the 
standard fraction .7854. By way 
of explanation we will dwell upon 
the above method for a short time. 
In Fig. 12 we have a surface which figure 12. 

measures one inch on all four 
sides, and which has an area of one square inch. 

Now in a circle which is contained in this figure, and 
which touches all four sides of the square, we would 
only have .7854 of a square inch. If the diameter of 
this circle is 2 in., instead of i, you can readily see by 
Fig. 13 that its area is four times as great or 2 x 2 = 4. 
We then multiply by the standard number .7854 in 
order to find the area contained in the two-inch circle; 
and if the diameter were 3 in., then 3x3=9, and 
9 X .7854 would be the area in square inches contained 
in the three-inch circle. 

Again, if we had a square one inch in area, like Fig. 
14, and we took one leg of a carpenter's compass and 
placed it on one corner of this square, striking a 




26 



ELECTRICITY FOR ENGINEERS 



quarter-circle from one adjacent corner to the other 
adjacent corner, the area inscribed by the compass 
would again be .7854 of a square inch. 

The above will explain to the reader the relation 



r 1 1 

. ^^ --^ 



FIGURE 13. 

between the circular and square mil. The circular 
mil is a circle one mil (-^ q-V-o- of an inch) in diameter. 
The square mil is a square one mil long on each side. 
In the calculation of wires for electrical purposes, the 
circular mil is generally used, because we need only 
multiply the diameter of a wire by 
itself to obtain its area in circular 
mils. If we used square mils we 
should have to multiply by .7854. 

The resistance of a conductor 
(wire) increases directly as its length, 
and decreases directly as its diameter 
is increased. A wire having a diam- 
eter of one mil and being one foot 
long has a resistance at ordinary temperature of 10. 7 
ohms. If this wire were two feet long, it would have 




FIGURE 14. 



ELECTRICITY FOR ENGINEERS 97 

a resistance of 21.4 ohms, but if it were two mils in 
diameter and one foot long, it would have a resistance 
one-fourth of 10.7, or about 2.67. 

Every transmission of electrical energy is accom- 
panied by a certain loss. We can never entirely pre- 
vent this loss any more than we can entirely avoid 
friction. But we can reduce our loss to a very small 
quantity simply by selecting a very large wire to carry 
the current. This would be the proper thing to do if 
it were not for the cost of copper, which would make 
such an installation very expensive. As it is, wires 
are usually figured at a loss of from 2 to 5 per cent. 

The greater the loss of energy we allow in the wires 
the smaller will be the cost of wire, since we can use 
smaller wires with the greater loss. 

In long distance transmission and where the quality 
of light is not very important, a loss of 10 or 20 per 
cent, is sometimes allowed, but in stores, residences, 
etc., the loss should not exceed 2 or 3 per cent., other- 
wise the candle power of the lamps will vary too much. 

Where the cost of fuel is high the saving in first cost 
of copper is soon offset by the continuous extra cost 
of fuel to make up for the losses in the wires. 

To determine the size of wire necessary to carry a 
certain current at a given number of volts loss, we may 
proceed in the following manner: Multiply the num- 
ber of feet of wire in the circuit by the constant 10.7, 
and it will give the circular mils necessary for one ohm 
of resistance. Multiply this by the amperes, and this 
will give the circular mils for a loss of one volt. Divide 
this last result by the volts to be lost, and the answer 
will be the number of circular mils diameter that a 
copper wire must have to carry the current with such a 
loss. After obtaining the number of circular miis 



28 ELECTRICITY FOR ENGINEERS 

required, refer to the table of circular mils, and select 
the wire having such a number of circular mils. 
The formula is as follows: 

Feet of wire x 10.7 x amperes . , ., 

;rT-r. — ^ = circular mils. 

Volts lost 

By simply transposing the above terms we obtain 
another formula, which can be used to determine the 
volts lost in a given length of wire of a certain size, 
carrying a certain number of amperes. 

The formula is as follows: 

Feet of wire x 10.7 x amperes _ tt 1. 1 
Circular mils 

And again, by another change in the terms we 
obtain a formula which shows the number of amperes 
that a wire of given size and length will carry at a 
given number of volts lost: 

Circular mils x volts lost . 

^ — = Amperes. 

reet or wire xio.7 

In computing the necessary size of a service or main 
wire, to supply current for either lamps or motors, it 
is necessary to know the exact number of feet from the 
source of supply to the center of distribution. When 
the distance of center of distribution is given it is well 
to ascertain whether it is the true center or not. It 
may be only the distance from a cut-out box that has 
been given, when it should have been the distance 
from the point at which the service enters the building 
or, perhaps, from the point at which the service is con- 
nected to the street mains. For when the size is deter- 
mined it is for a certain loss which is distributed over 
the entire length of the wire to be installed. The trans- 
mission of additional current on the mains in the build- 
ing increases the drop in volts in the main, and likewise 



ELECTRICITY FOR ENGINEERS 29 

in the service. Most buildings are wired for a certain 
per cent loss in voltage, estimated from the point 
where the service enters the building. All additions 
should be estimated from that point. 

In using the formula for finding the proper size wire 
to carry current, the first thing to be determined is the 
length of the wire; remember that the two wires are in 
parallel, and therefore the total length of the wire is 
twice the total distance from the commencement to 
the end of the circuit. If the proposed load on this 
circuit is given in lamps, you may reduce it to amperes, 
and if the proposed load is given in horsepower, you 
may reduce it to amperes. The voltage on the circuit 
is known in either case. You take the loss of the 
voltage and divide the product of amperes, multiplied 
by the length, as found, and 10.7 by it; this answer 
will be the size in circular mils of a wire necessary to 
carry the amperes. 

Example: What is the size of wire required for a 50 
volt system, having 100 lamps at a distance of 100 ft., 
with a 4 per cent loss? 

Afiswer: The load of 100 lamps on a 50 volt system 
is 100 amperes, and a 4 per cent loss of 50 volts is 2 
volts. Multiply the total length of the wire, which is 
twice the distance, or 200 ft., by the 100 amperes of 
current; this gives us 20,000. Then multiply this by 
the constant, which is 10.7; this gives us 214,000. 
Divide this by 2, which is the loss in volts, and you 
have 107,000 circular mils diameter of wire required 

When determining the size of wire to be used it is 
always necessary to consult the table of carrying 
capacities, and this will very often indicate a wire 
much larger than that determined by the wiring for- 
mula, especially if a somewhat high loss is figured on. 



so ELECTRICITY FOR ENGINEERS 

When estimating the distance it is not always cor* 
rect to take the total distance. 

To illustrate: Suppose one lamp is lOO ft. from the 
point at which the distance is determined, and the 
farthest lamp is 400 ft., the remaining lamps being 
distributed evenly between these two points; we would 
average the distances between the first and last lamp, 
which would be 200 ft. It is necessary to use judg- 
ment in estimating the mean or average distance, as 
the lamps or motors are bunched differently in each 
case 

In a series system the loss in voltage makes con- 
siderable difference to the power, but does not affect 
the quality of the light as much as in a multiple arc or 
parallel system. In a parallel system the lamps 
require a uniform pressure, and this can only be had 
by keeping the loss low. In a series system the lamps 
depend upon the constant current and the voltage 
varies with the resistance, in order to keep the current 
constant. This is accomplished by a regulator on the 
dynamo, which is designed to compensate for the 
changes of resistance in the circuit and to increase or 
decrease the pressure as required. 

in estimating the size of wire for a series system you 
consider the total length of the loop. There is no 
average distance as the total current travels over the 
entire circuit. We will assume that you have an arc 
light circuit of a No. 6 Brown & Sharp gauge wire and 
want to find what loss there is in this circuit. You 
have the area of a No. 6 wire, which is 26,250 circular 
mils, and the length of the circuit, and from this we 
will figure the loss in this manner: Assuming the 
circuit to be 10,000 ft. long, and the current 10 
amperes, we will multiply 10,000 ft. by 10 amperes, 



ELECTRICITY FOR ENGINEERS 



SI 



And this by 1.07, which gives us 1,070,000, and divide 
this b}^ 26,250. The answer is 40 volts, lost in the 
circuit. 








i(ee^ bva\> S^owv cQ-nXacl u)v\:\\ u)We 







Such a circuit would operate at perhaps 2,000 or 
3,000 volts, and a loss of 40 volts would not be exces- 



32 ELECTRICITY FOR EISGINEERS 

sive. It would be wasting a little less energy than is 
required to burn one large arc lamp. 

The multiple series system is a number of small wires 
connected in multiple, and is the same as the multiple 
arc or parallel system. The wire is figured in the same 
Woy as for the multiple arc system. 

The series multiple system is a number of small paral- 
el systems, and these are connected in series by the 
main wire. The wire is figured the same as for the 
series system. 

The Edison three-wire system is a double multiple, and 
the two outside wires are the ones considered when 
carrying capacity is figured. When this system is 
under full load or balanced, the neutral wire does not 
carry any current, but the blowing of a fuse in one of 
the outside wires may force the neutral wire to carry 
as much current as the outside wire and it should, 
therefore, be of the same size. The amount of copper 
needed with this system is onl}^ three-eighths of that 
required for a two-wire system. 

Wiring Tables. On the following pages are presented 
-wiring tables for 110,220 and 500 volt work. These 
tables are used in the following manner: Suppose We 
wish to transmit 60 amperes a distance of 1,800 ft. at 
no volts and at a loss of 5 per cent. We take the col- 
umn headed by 60 in the top row and follow it down- 
ward until we come to 1,800, or the number nearest to 
it. From this number we now follow horizontally to 
the left, and under the column headed by 5 we find 
the proper size of wire, which is 500,000 c. m. The 
same current, at a loss of 10, would require only a 0000 
wire, as indicated under the column at the left, headed 
by 10. 

Before making selection of wire, always consult the 



ELECTRICITY FOR ENGINEERS 33 

table of carrying capacities, page 38. This table is 
taken from the rules of the National Board of Fire 
Underwriters, and is in general use. 

The first three of the following tables are wiring 
tables for the three standard voltages, no, 220, 50G 
From these tables can be found the sizes of wire 
equired to carry various amounts of current (in am- 
pe^es) different distances (in feet) at several percent- 
ages of loss, or the distance the different sizes of wire 
will carry various amounts of current at several per- 
centages of loss can be found. 

These tables are figured on safe carrying capacity for 
the different sizes of wire. The distances in feet are 
to the center of distribution. 



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S8 



ELECTRICITY FOR ENGINEERS 



TABLE OF CARRYING CAPACITY OF WIRES. 

UNDEBWRITEBS' RULES. 



B &S. G. 

i8. 
i6. 

14. 
12. 
10. 

8. 

6. 

5. 

4. 

3. 

2. 

I. 

o. 

00. 

000. 

0000. 



Table A. 

Rubber 

Insulation. 

Amperes. 

3 

6.... 
12 

. . 17.... 

.. 24.... 

... 33 

... 46.... 

. . 54.... 

.. 65.... 
... 76.... 

.. 90.... 
, . . 107 ... . 

.. 127.... 
... 150.... 

. . 177.... 

. . 210. . , . 



Circular Mils. 

200,000 200. 

300,000 270 . 

400,000 330. 

500,000 390. 

600,000 450. 

700,000 500. 

800,000 550. 

900,000 600. 

1,000,000 650. 

1,100,000 690. 

1,200,000 730. 

1,300,000 770. 

1,400,000 810. 

1,500,000 850. 

1,600,000 8qo. 

1,700,000 930. 



Table b. 

Other 
Insulations. 
Amperes. 



It). 
23. 



1,800,000 970 1,550 

1,900,000 1,010 1,610 

2,000,000 1,050 1,670 



Circular 

Mils. 

1,624 
2,583 
4,107 
6,530 

32 10,380 

46 16,510 

t)5 26,250 

77 33,100 

92 41.740 

no 52,630 

131.. 66,370 

156 83,690 

185 105,500 

220 133,100 

262 167,800 

312 211,600 

. 300 
. 400 
. 500 
. 590 
. 680 
. 760 
. 840 
. 920 
.1,000 
.1,080 
.1,150 
.1,220 
.1,290 
.1,360 
.1,430 
.1,490 



The lower limit is specified for rubber-covered wires 
to prevent gradual deterioration of the high insula- 
tions by the heat of the wires, but not from fear of 
igniting the insulation. The question of drop is not 
taken into consideration in the above tables. 



ELECTRICITY FOR ENGINEERS 



39 



TABLE OF DIMENSIONS OF PURE COPPER WIRE.* 







Arf^Ji- 


Weight and Length. 


No. 


Diam. 
Mils. 








Sp. Gr. 8.9. 




B. & S. 


Clrcular 


Square 


Lbs. 


Lbs. 


Feet 






Mils. 


Mils. 


per 
1000 feet. 


per 
Mile. 


per 
Pound. 


0000 


460.000 


211600.0 


166190.2 


640.73 


3383.04 


1.56 


000 


409.640 


167805.0 


131793.7 


S-08.12 


2682.85 


1.97 


00 


364.800 


133079.0 


104520.0 


402.97 


2127.66 


2.48 





324.950 


105592.5 


82932.2 


319.74 


1688.20 


3.13 


1 


289. aoo 


83694.5 


65738.5 


253.43 


1338.10 


3.95 


2 


257.630 


66373.2 


52129.4 


200.98 


1061.17 


4.98 


3 


229.420 


52633.5 


41338.3 


159.38 


841.50 


6.28 


4 


204.310 


41742.6 


32784.5 


126.40 


667.38 


7.91 


5 


181.940 


33102 2 


25998.4 


100.23 


529.23 


9.98 


6 


162.020 


26250.5 


20617.1 


79.49 


419.69 


12.58 


7 


144.280 


20816.7 


16349.4 


63.03 


332.82 


15.86 


8 


128.490 


16509.7 


12966.7 


49.99 


263.96 


20.00 


9 


114.430 


1H094.2 


10284.2 


39.65 


209.35 


25.22 


10 


101.890 


10381.0 


8153.67 


31.44 


16.5.98 


31.81 


11 


90.742 


8234.11 


6467.06 


24.93 


137.65 


40.11 


12 


80.808 


6529.94 


5128.60 


19.77 


104.40 


50.58 


13 


71.961 


5178.39 


4067.07 


15.68 


82.792 • 


63.78 


14 


64.084 


4106.76 


3225.44 


12.44 


65.658 


80.42 


15 


57.068 


32.56.76 


2557.85 


9.86 


52.069 


101.40 


16 


50.820 


2582.67 


2028.43 


7.82 


41.292 


127.87 


17 


45.257 


2048.20 


1608.65 


6.20 


32.746 


161.24 


18 


40.303 


1624.33 


1275.75 


4.92 


25.970 


203.31 


19 


35.890 


1288.09 


1011.66 


3.90 


20.594 


256.39 


20 


31.961 


1021.44 


802.24 


3.09 


16.331 


323.32 


21 


28.462 


810.09 


636.24 


2.45 


12.952 


407.67 


22 


25.347 


642.47 


504.60 


1.95 


10.272 


514.03 


23 


22.571 


509.45 


400.12 


1.54 


8.1450 


648.25 


24 


20.100 


404.01 


317.31 


1.22 


6.4593 


817.43 


95 


17.900 


320.41 


251.65 


.97 


5.1227 


1030.71 


26 


15.940 


254.08 


199..^6 


.77 


4.0623 


1299.77 


27 


14.195 


201.50 


158.26 


.61 


3.2315 


1638.97 


28 


12.641 


159.80 


125.50 


.48 


2.5548 


2066.71 


29 


11.257 


126.72 


99.526 


.38 


2.0260 


2606.13 


80 


10.025 


100.50 


78.933 


.30 


1.6068 


3286.04 


31 


8.928 


79.71 


62.603 


.24 


1.2744 


4143.18 


32 


7.950 


63.20 


49.639 


.19 


1.0105 


5225.25 


33 


7.080 


50.13 


39.36^ 


.15 


.8015 


6588.33 


34 


6.304 


39.74 


31.218 


.12 


.6354 


8310.17 


36 


5.614 


31.52 


24.^53 


.10 


.5039 


^J4;8.46 


36 


5.000 


25.00 


19.635 


.08 


.3997 


:3209.98 


37 


4.453 


19.83 


15.574 


.06 


.3170 


16654.70 


38 


3.965 


15.72 


12.347 


.05 


.2513 


21006.60 


39 


3.531 


12.47 


9.7923 


.04 


.1993 


26487.84 


40 


3.144 


9.88 


7.7635 


.03 


.1580 


33410.05 



♦1 mile puie copper wire 13..59 ohms at 15.5® C. or 

1-16 in. diam. — 59.9« F. 



1 circular mil is .7854 square mil. 



CHAPTER III 

Current Generation in Dynamos — Dynamos — Brushes and 
Commutators. 

Cnrrent Generation in Dynamos. If we take a coil of 
wire, Fig. 15, and rapidly thrust a magnet into it, we 
shall observe a certain deflection of the galvano- 
meter needle shown with it. This deflection con- 
tinues only while the magnet is in motion. After 




FIGURE 15. 



we have inserted the magnet and it has come to 
rest the galvanometer needle will return to its normal 
position. When we withdraw the magnet the deflec- 
tion of the needle will be in the opposite direc- 
tion. If the magnet is inserted or withdrawn with 
a very quick motion, the deflection will be consider- 
able. If the magnet is very slowly inserted or with- 
drawn the deflection will hardly be noticeable. The 

40 



ELECTRICITY FOR ENGINEERS 



41 



same phenomena will occur if instead of moving the 
magnet, we hold it stationary and move the coil, or if 
both of them be moved towards or from each other. 
The deflection of the compass needle indicp.tes that a 
current of electricity is passing along thj wire, and the 
experiments above described show exactly how cur- 
rents of electricity are produced in dynamos. 

An electromotive force is induced by rapidly cutting 

''lines of force,'* that is, by moving either a magnet 

over a wire or a wire over or near a magnet. The 




FIGURE 16. 



current in turn is the result of this electromotive force 
acting in a closed circuit. A bar of iron becomes an 
electromagnet if we wind about it a few turns of wire 
and cause a current of electricity to flow along the 
wire, Fig. i6. The magnetism is conceived to consist 
of lines of force, which leave the bar at one end and 
enter it at the other, the direction of these lines 
depending upon the direction in which the current 
circulates about the bar of iron. The number of these 
lines of force depends upon the number of ampere 
turns in the iron bar and on the diameter, length and 
quality of the iron bar. 



42 ELECTRICITY FOR ENGINEERS 

Ampere turns is a term used to indicate the mag- 
netizing force; it is the number of turns of wire on a 
magnet multiplied by the current in amperes flowing 
through these turns of wire. 

Haskins, in Electricity Made Simple, explains this 
thus: "If, for instance, we have a current of one 
ampere flowing through a single turn of wire around a 
bar of soft iron and we have developed enough mag- 
netism to lift a keeper or other piece of iron, weighing 
one ounce, then with one-half the amount of current 
and two coils around the bar, we would obtain the 
same result, and with three turns of wire we would 
require but one-third the current to develop the same 
lifting power in the bar or magnet." 

The law of magnetic flow is very much the same as 
the law of current flow. If the iron bar is of low mag- 
netic resistance, the flow will be quite great; if of high 
resistance, the flow will be small. 

Lines of force can also be shunted just as a current 
of electricity can; that is, they will follow the path of 
lowest resistance just as a stream of water or a current 
of electricity will. 

Now let us consider the elementary sketch of a 
dynamo. Fig. 17. The wire a represents the armature 
and we have also the iron bar and the coil of wire 
wound on it and, for the present, we may consider the 
battery B as the source of the current which produces 
the magnetism or lines of force in the iron bar. The 
battery current magnetizes the iron bar (which in 
dynamos is known as the field magnet) and produces 
the lines of force indicated by arrows. 

These lines of force leave the field magnet of our 
dynamo at the north pole marked N, and pass through 
the air-gap and armature into the south pole marked S, 



ELECTRICITY FOR ENGINEERS 43 

As we begin to move the wire or armature, it cuts 
through these lines of force and begins to generate an 
electromotive force, which in turn will cause the cur- 
rent to flow if the circuit is closed through a lamp or 
other device. 

This current reverses in direction as the wire a passes 
from the influence of the south pole into that of the 
north pole and the brushes B' and B", which transmit 




FIGURE 17. 



the current to the outside wires, are so set that they 
change the connection of the wire a at the time that it 
passes from one pole to the other. By this means the 
current in the externa! circuit is kept constant in 
direction, although it alternates in the armature. 

The faster we turn our wire or armature, the greater 
will be the electromotive force generated. Instead of 
using only one wire, as in Fig. 17, we may take many 



44 



ELECTRICITY FOR ENGINEERS 



turns before bringing the end out, and in so doing 
obtain the well known drum armature, or, by a slightly 
different method of winding, the gramme ring arma- 
ture, Fig. i8. Here we have many wires cutting the 
lines of force at once and our electromotive force with 
the same number of revolutions of the armature is cor- 
respondingly increased, and the more turns of wire we 
arrange to cut those lines of force per second the 
greater will be our E. M. F. Instead of providing 




FIGURE 18 



more wire or increasing the speed of our armature we 
can increase the magnetism, or number of lines of force, 
by sending more current through the fields, that is 
increasing the "ampere turns/' 

If we wish to reverse the current flow we can do so 
by revolving the armature in the opposite direction, 
or by reversing the current through the fields. 

Dynamos. Having so far considered the generation 
of currents in dynamos, we may now consider different 
types of dynamos and their uses. Fig. 19 shows adia- 



ELECTRICITY FOR ENGINEERS 



45 



gram of the wires and connections of a series dynamo. 
The principal use of this dynamo at present is in con- 
nection with series arc circuits. (See Fig. 7.) Thi:: 
dynamo is usually equipped wath an automatic regu • 
•ator (which will be explained later) to raise or lower 
he voltage as the number of lamps increases or 




FIGURE 19. 



CiCcreases, the current remaining constant at abouc 10 
amperes. By reference to the figure, we can trace the 
current as it flows from the -h brush, in the direction of 
the arrows, around both field magnets and through the 
lamps, returning to the — brush on the dynamo. In 
our elementary sketch of a dynamo we used battery 
current to magnetize our fields; we need not consider 



46 



ELECTRICITY FOR ENGINEERS 



that any more, for in practice all direct current 
dynamos produce their own magnetism by circulating 
some or all of their current through the field coils. 

In the shunt wound dynamo, Fig. 20, the wire in the 
field winding is of such size and connected in such a 
manner as to have a resistance so high that only a 




(TtntTfT) 



FIGURE 20. 



portion of the main generated current of electricity 
passes around the field magnets. The quantity of cur- 
rent passing around these field magnets is also regu- 
lated by a resistance sometimes called a rheostat shown 
at R. The resistance to the flow of current through 
this box is adjusted by hand by the attendant and the 
flow of current through this rheostat and around the 



ELECTRICITY FOR ENGINEERS 47 

field magnet is what determines the electromotive force 
of the dynamo. 

This type of dynamo is used for electric lighting and 
for operating motors. The electromotive force of such 
a dynamo remains nearly constant, but the current 
varies with the number of lights or motors used. If it 
were connected to too many lights it v/ould deliver too 
much current and become overheated and perhaps 
burn out. The current leaves at the + brush, passes 
through whatever lamps happen to be switched on and 
returns to the — brush. 

Fig. 21 shows a diagram of a compound wound 
dynamo. This is really a combination of the series 
and shunt dynamos. If the current in a series dynamo 
is not kept constant the magnetism in the fields will 
vary as the current varies, and consequently its volt- 
age will be very unsteady. This makes such a dynamo 
unfit tor use with variable currents. 

The voltage of a shunt dynamo is quite constant with 
variable loads, but still it leaves much room for 
improvement; not because of any variation in the 
induced electromotive force, but because of the losses 
occurring in the armature and wires conveying current. 
The loss of voltage in the armature and line equals the 
current multiplied by the resistance; consequently, as 
the current increases more and more volts are lost and 
the pressure goes down. If we would have the pressu;^ 
remain at its normal value, we must find some way to 
increase the field magnetism as the current delivered 
by the dynamo increases, and this is the purpose ot 
the compound winding. The compound winding car- 
ries the total current of the dynamo around the fields, 
but only a few times, just often enough so that the 
increase in magnetism resulting from this current may 



48 



ELECTRICITY FOR ENGINEERS 



make up tor the loss in the armature or line. Dyna- 
mos may be compounded for any per cent, of los? 
desired. 

The foregoing descriptions are those of direct cu* 
rent dynamos, and they are called direct or continuous 




FIGURE 21. 



current dynamos because the current flow continues m 
one direction out of the positive or -i- side of the 
dynamo, to the external circuit, and back again to the 
negative or - side of the dynamo. The current as it 
is generated in the coils of the armature which 



ELECTRICITY FOR ENGINEERS 49 

revolves between the field or pole pieces, is alter- 
nating; that is to say, if the armature wires were con- 
nected to collector rings the current in the outside 
wires would be reversed every time the position of the 
wire in the armature were changed from the influence 
of one pole piece to that of the other. If the coils 
constituting the armature are connected to a device 
called the commutator, they will be commutated or 
rectified. 

Such a commutator is formed of alternate sections of 
conducting and non-conducting m_aterial, running 
parallel with the shaft with which it turns. It is 




FIGURE 22. 

placed on the shaft of the armature so that it rotates 
with it, as shown in Fig. 22. The brushes press upon 
its surface and collect the current from the bars. (See 
Fig. 31.) The function of the commutator is to change 
the connections of the armature coils from the + or 
positive to the negative or — side of the circuit at the 
time at which the coil connected to the bar under the 
brush passes from the influence of one pole piece into 
that of the other. This is the time at which the cur- 
rent in the coil reverses in direction, and is called the 
neutral point. If we consider, for the sake of simplic- 
ity, an armature having only one turn of wire on it, 
as Fig. 17, there will be a time while the coil is in the 



50 ELECTRICITY FOR ENGINEERS 

position indicated by dotted lines at c and ^when no 
current is being generated. The brushes on any 
dynamo should always be set at this point, for this is 
the point of least sparking. In actual practice all 
commutators have quite a number of bars and it is 
impossible to avoid, in passing uncc ' the brushes, that 
at least two of them are in contact with a brush at the 
same time. If a brush did leave one bar before it 
touches another, the current would be enti/iely broken 
for that length of time and much sparking would 
result. The nature of all armature windings is such 
that while the brush is in contact with the commutator 
bars it short circuits that coil between them^. This is 
the main reason why the brushes must be kept at a 
point at which the coil which is short circuited gener- 
ates no current. 

Although the electromotive force generated in one 
coil of a dynamo is very small, the resistance of the 
**short circuit" formed by the dynamo brush is also 
very small and therefore the current may be quite large. 
This current is the main cause of sparking in dynamos. 
The number of bars constituting a commutator depends 
upon the winding of the armature, and the number of 
coils grouped thereon. By increasing the number of 
coils and commutator sections the tendency to spark 
at the brushes is decreased, and the fluctuations of the 
current are also decreased. However, there are many 
reasons against making the number of bars on a com- 
mutator very great. Increasing the number of bars in 
a commutator increases the cost of manufacture, and 
in smaller dynamos if the number of bars be increased 
beyond a certain extent, each bar becomes so thin 
that a brush of the proper thickness to collect the cur- 
rent from the commutator would lap over too many 



ELECTRICITY FOR ENGINEERS 51 

bars of the commutator at one time. Each commu- 
tator bar should be of the size that will present suffi- 
cient metal for the carrying capacity of the current 
generated in the coil to which it is connected. Differ- 
ent builders of dynamos have different ideas as to the 
number of amperes that maybe carried per square inch 
in a commutator bar, but where a commutator is made 




FIGURE 23. 

of 95 per cent, copper it is usual to allow for each lOO 
amperes a commutator bar surface oi i}4 sq. in. 

The method of electrical connection between the 
commutator bar and the coil of the armature varies in 
different designs. Some builders solder the terminals 
of the coils to the commutator bars; others bolt the 
terminals of the coils to the bars; and some makers 
use hard drawn copper and *'form" the armature coil 
in such a manner that both ends of the coil become 



52 ELECTRICITY FOR ENGINEERS 

commutator bars, making the coil continuous from one 
end of the commutator bar to the end of the diametric- 
ally opposite commutator bar. 

In Fig. 23 we show a so-called "formed" armature 
coil, after it has been prepared by properly insulating 
it and bending it into shape ready to be applied to the 
laminated armature body. 

In Fig. 24 is shown a ''formed" coil armature with 



FIGURE 24:. 



the winding almost finished. The commutator is yet 
to be placed on the shaft and the coil terminals con- 
nected to the commutator bars. 

In Fig. 25 we have an armature shaft with the lami- 



FIGURE 25. 

nated armature body keyed on to the shaft ready to be 
wound. 



EI.1.CTRICITY FOR ENGINEERS 58 

The body on which the armature coils are to be 
wound is made up of sheet iron punchings and placed 
on the armature shaft in the same manner that you 
would put ordinary iron washers on a lead pencil. 
These punchings or discs are insulated from one 
another by having previously been painted with a coat 
of shellac; for there is the same tendency to produce 
current in the iron part of the armature, due to the 
cutting of the magnetic lines, as there is in the copper 
wire which is wound on its surface. If the iron core 
were solid, there would be a very large current circu- 
lating in the same direction as that which flows through 
the wires. Such a current would be entirely useless 
and would heat the armature; to prevent this the 
armature is built up of thin sheet iron discs. 

Brushes and Commutators. Figs. 26 to 30 show differ- 
ent arrangements of modern brushes and brush-holders. 
These are used to take the current from the commu- 
tator and deliver it to the outside wires in the case of a 
dynamo, and for the opposite in the case of a motor. 

There are many different designs and constructions 
of brushes and brush-holders, and these designs are 
brought about by the various ideas of different builders 
in their attempt to produce various advantageous 
results, but the electrical connections and underlying 
principles remain the same whether a copper or a car- 
bon brush be used. 

In any construction of brush holding device, if great 
care is not exercised in keeping it thoroughly clean, 
trouble is sure to be the result, and trouble of this 
nature increases so rapidly that unless the attendant 
immediately sets about to right it, a burned out arma- 
ture is almost sure to be the consequence sooner or 
later. In alternating current dynamos, where br'ishes 



54 



ELECTRICITY FOR ENGINEERS 



rest on collector rings instead of commutators, it is 
much easier to keep out of trouble, because the 
brushes in this case merely collect the current from 
the rings and do not commutate or rectify it. 

The brushes and commutator of a dynamo or motor 




FIGURE 26. 



are probably the most important parts with which the 
engineer has to deal. Great care should be taken that 
the brushes set squarely on the commutator and that 
the surface of the brushes and commutator are as 
smooth as possible. It is a good plan, and in some 



ELECTRICITY FOR ENGINEERS 



55 



cases the brush-holders are so made, that the brushes 
set in a staggering position, that is to say, in a posi- 
tion so that all the brushes will not wear in the same 
place over the circumference of the commutator and 



'j:rr4^f^- 




FIGURE 27. 

:ause uneven wear across the length of the commutator 
bars. In most machines the armature bearing is left 
so that there is more or less side motion, which, when 
the armature is running, causes a constant changing of 
the position of the brushes and commutator. 



56 



ELECTRICITY FOR ENGINEERS 



Whatever style of brush is used, the commutator 
should be kept clean and allowed to polish or glaze 
itself while running*. No oil is necessary unless the 
brushes cut, and then only at the point of cutting. A 
cloth (not cotton waste) slightly greased with vaseline 
and applied to the surface of the commutator while 




FIGURE 28. 



running is best for the purpose of preventing the com- 
mutator from cutting. Should the commutator become 
rough, it should be smoothed with sandpaper, never 
vising emery cloth, because emery cloth is conductor 
of electricity, and the particles of emery are liable 
to lodge themselves between the commutator bars 
in the mica and short circuit the two bars, thereby 



ELECTRICITY FOR ENGINEERS 57 

Durning a small hole wherever such a particle of emery 
^as lodged itself. The em.ery will also work into the 
Drushes and copper bars and wear them down; it being 
almost impossible to remove all the emery. 

In the end-on carbon brushes, Fig. 30, the contact 
surface of the brushes should be occasionally cleaned 
Dy taking a strip of sandpaper, with the smooth side 
:>i the paper to the commutator, and the sanded side 
:oward the contact surface of the brush, and then by 




K.GURK 29. 

eaving the tension of the brush down on the sand- 
paper, it is an easy matter to move the sandpaper to 
uid fro and throughly clean off the glazed and dirty 
;urface from the carbon, leaving it with a concave thai 
vill exactly fit the commutator. 

The advantages of carbon brushes are many. 
\mong the cardinal points are: The armature may 
un in either direction without it being necessary to 
dter the brushes; the carbon can be manufactured with 
I quantity of graphite in its construction, thereby 



58 



ELECTRICITY FOR ENGINEERS 



lowering the mechanical friction of the brushes on the 
commutator ; they do not cut a commutator so much 
by sparking; the commutator has a longer life, the wear 
being more evenly distributed. 

Carbon brushes, due to their rather high resistance^ 
will often heat up considerably, but, although this 
heat is objectionable, their resistance tends to cut 
down the sparking. The brushes are sometimes coated 
with copper to reduce their resistance. Often a car- 



X 







-^*^^^rt,w.i. 



FIGUEE 30. 



bon brush will be found which is very hard. As a rule 
such a brush should be thrown away, as it will heat 
abnormally and at the same time wear the commu- 
tator. 

In Fig. 31 we have one of the various so-called old 
styles of leaf brush-holders. The end-on brushes are 
more generally used in modern practice, because their 
contact surface area is not increased or decreased by 
wear. Consequently the brushes always remain in a 
diametrically opposite position. With the old style 



ELECTRICITY FOR ENGINEERS 



59 



brush-holding device, where the brushes rest on the 
commutator at a tangent, great care should be exer- 



\ 1 


\ 

\ 


1/ B 




FIGURE 31. 



cised not to allow the brushes to wear in a position sc 
that their points will be out of diametrical opposition. 







FIGURE 32. 

In Fig. 31 we show the correct way that this tvpe of 
brush should be set. 



60 



ELECTRICITY FOR ENGINEERS 



In Figs. 32 and 33 we show the incorrect way. 

By remembering that each one of the commutator 
bars is the end of a coil, and then just mentally tracing 
the current through the coils from one brush to the 
other, we can readily understand what the results are 
when the brushes are neglected and left in a relative 
position, as shown in these figures. 

Sparking is the usual result of brashes allowed to 
wear to such an extent. Overloading of a dynamo or 
motor will also cause serious sparking, and no amount 




of care can prevent damage to armature, commutator 
or brushes, if a machine is permitted to be overloaded 
Sometimes the commutator will contain one or more 
bars which, as the commutator gets old and wears 
down, will wear away either too fast or too slow, due 
to the metal being harder or softer than the rest of the 
bars forming the commutator. This causes a rough- 
ness of the commutator and results in the flashing of 
the brushes and heating of both the commutator and 
brushes. About the only satisfactory method of 



ELECTRICITY FOR ENGINEERS 



61 



remedying this evil is to take out the armature and 
have the commutator turned down in a lathe. 

A short-circuited coil in the armature, or a broken 
armature connection, will also cause considerable 
sparking. Either of these conditions can be located 
by means of a Wheatsone bridge or by what is known 
as the fall of potential method. To make a test with 
this latter method, connect in series with the armature 
to be tested some resistance capable of carrying the 
necessary current, also an ammeter. Some apparatus 
for varying the current strength, such as a water rheo- 



t^^eM 9 



WR 



AAAAAr-O 




FIGURE 34. 



Stat or lamp rack, must be connected in the circuit, a 
diagram of which is shown in Fig. 34. 

In the diagram, WR is the water rheostat or lamp 
rack, R the known resistance, A the ammeter and M 
the armature to be tested. By means of the water 
rheostat regulate the current passing over the appa- 
ratus until it is of such strength that a deflection can 
be obtained on a voltmeter when it is connected to two 
adjacent bars on the commutator. Suppose the arma- 
ture coil between bar i and 2 on the commutator were 
broken. The voltmeter connected across these two 
bars would give the same reading as when connected 



62 ELECTKICITY FOR ENGINEERS 

across the two points lo and ii. If the voltmeter were 
connected between any other two points on the com- 
mutator on the same side as the broken coil no deflec- 
tion would be obtained, while connecting the voltmeter 
between any two adjacent bars on the other side of the 
commutator would give practically the same reading 
irrespective of which bars were used. The resistance 
of one or more sections of the armature winding could 
also be found by using Ohm's law, R = E/C, or the 
resistance would be equal to the voltage divided by the 
current as shown on the ammeter. It must be remem- 
bered that this latter will be true only when there is an 
open coil in one side of the armature, for in this case 
only will the whole current flow through the one side. 
If the coil between bars i and 2 were short circuited, 
the voltmeter would show practically no reading 
between these bars; while between any other bars some 
deflection would be obtained. An open circuit or 
short circuit will nearly always be found by examina- 
tion, as the trouble usually happens very close to the 
commutator connections in the case of an open circuit 
and may very often be found between the commutator 
bars themselves, in the case of a short circuit. If the 
trouble is not at these places it will usually be in the 
windings, in which case the only remedy is to have it 
re-wound. Temporary repairs may be made in the case 
of an open circuit by short circuiting the commutator 
bars around the open circuit, but this method should 
only be used in emergency, as the sparking will in time 
destroy the commutator. 

With many dynamos, especially of older types, it is 
necessary to shift the brushes with every change of 
load. The current produced by the armature makes a 
magnet out of it and the magnetism of the armature 



ELECTRICITY FOR ENGINEERS 



63 



opposes that of the fields. In Fig. 35 the armature is 
working with a very light load and the lines of force 
of the field magnets are only slightly opposed by those 




FIGURE 35. 

of the armature. In Fig. 36 we assume a heavy load 
on the dynamo and consequently the magnetism of the 
armature opposes that of the fields. This changes the 
location of the neutral point (when the coils under the 
brush generate no current) and it becomes necessary to 




FIGURE 36. 



shift the brushes accordingly, or great sparking would 
result. The amount of shifting necessary with changes 
of load varies in different dynamos. If the field is 



64 ELECTRICITY FOR ENGINEERS 

very strong compared to the armature, it will be bu«^ 
little. If the armature (as in some arc dynamos) is 
very strong compared to the field, it will be consider- 
able. 

In dynamos, with increasing load, the brushes should 
::e shifted in the direction of rotation and in the oppo- 
site direction when the load decreases. 

Never allow a dynamo or motor to stand in a damp 
place uncovered. Moisture is apt to soak into the 
windings and cause a short circuit or ground when 
started. Great care should also be used should it ever 
be found necessary to use water on a heated bearing. 
If the water is allowed to reach the armature or com- 
mutator, it is bound to cause trouble. Water should 
only be used in case of emergency, and then sparingly* 



CHAPTER IV 



OPERATION OF DYNAMOS 



Constant Potential Dynamos. In order to thoroughly 
explain the operation of dynamos, let us assume that 
we have the task of starting a new shunt dynamo, one 
that has never generated any current. Our first step is 
to open the main switch and turn the rheostat or field 




FIGURE 37. 



resistance box so that all the resistance is in circuit. 
A rheostat consists of a number of resistances. Fig. 37, 
so arranged that they can be cut in or out of the circuit 
without opening the circuit. By reference to the figure 
it will be seen that the current enters at the handle and 
from there passes to the contact point upon which the 

65 



66 



ELECTRICITY FOR ENGINEERS 



handiC happens to rest. If the handle is at i the cur- 
rent must pass through all the wire in the box; if it is 
at 2 it simply passes through the handle and out. 

Rheostats for the shunt circuit of a dynamo should 
have sufficient resistance, so that when it is all inserted 
the voltage of the dynamo will slowly sink to zero. 
Ihis method of stopping the action of a dynamo is 




FIGURE 37. 



perfectly safe and should be followed wherever pos- 
sible. 

We are now running our dynamo with all resistance 
in the shunt circuit. This is simply as an extra pre- 
caution because we know nothing about this particular 
dynamo. When it is known that the dynamo is in 
good order, the engineer or attendant usually cuts out 
all the resistance, and as the generator builds up or, in 
other words, generates current, he proceeds, by the aid 
of the resistance box, to cut down or diminish the flow 
of electi^'city around the field magnets of the dynamo, 



ELECTRICITY FOR ENGINEERS 67 

and thereby diminish the magnetic density of the 
field magnets and the electromotive force of the 
dynamo. 

We must now gradually turn our rheostat so as to 
cut out resistance and watch the voltmeter, which is 
connected as shown at V in Fig. 20, and receives cur- 
rent whenever the dynamo is operating. Suppose that 
the voltmeter indicates nothing, and we find that the 
dynamo will not generate. On examination of all the 
connections we find everything correct, and we now 
discover that the dynamo field magnets do not contain 
what is termed '^residual magnetism'' sufficient to start 
the process of generating current. 

Before an armature can generate current it must cut 
lines of force, that is, it must revolve in a magnetic 
field. If the dynamo has been generating current it is 
likely that the iron cores of the field magnets will 
retain sufficient magnetism to start the generation of 
current again. This magnetism which remains in the 
iron is known as residual magnetism. It will make 
itself manifest by attracting the needle of a compass, 
or if strong, a screw driver or a pair of pliers. If we 
find no magnetism in the iron core of the field mag- 
nets, we may take the ends of the shunt winding on the 
field magnets and pass current over them from a bat- 
tery. This current will produce sufficient magnetism 
to cause the generator to build up; in other words, if 
we disconnect these batteries, and connect the wires 
back again from where we got them, we will find that 
we can generate current with the machine. 

When the machine begins to generate, we watch the 
voltmeter and cut resistance in or out of the circuit 
according whether we need to lower or raise the volt- 
age. If we have only one dynamo we may close the 



68 ELECTRICITY FOR ENGINEERS 

main switch before we begin generating or after we 
have attained full voltage. 

Again referring to the pole pieces on the dynamo, it 
is possible that there is a sufficient quantity of residual 
magnetism in the pole pieces, and that the polarity of 
both field magnets, between which the armature is 
revolving, is the same. This would also cause the 
dynamo to fail in generating current. If sending bat- 
tery current^ through the coils does not make one field 
a north pole and the other a south pole, one of the 
fields must be connected wrong, and we must make 
some changes in the connection. 

Referring to Fig. 20, a and b are the terminals of the 
shunt winding on the fields. If the winding of the 
fields is correctly put on it will be as in the little sketch 
at lower corner; that is, if both field magnets were 
taken out of their places and put together, the wind- 
ing should run as one continuous spool. But if the 
winding on one field is wrong, we need simply change 
its connection, as, for instance, transferring c to a and 
a to c. 

In order that a dynamo may excite itself, it is neces- 
sary that the current produced by the residual magnet- 
ism shall flow in such a direction as to strengthen this 
residual magnetism. If the current produced by the 
residual magnetism flows through the field coils in the 
opposite direction this will tend to weaken the residual 
magnetism and consequently to reduce the current 
which flows. 

For this reason if the first attempt to start a dynamo 
with battery current fails, the battery should be applied 
with the opposite poles so that the magnetism it pro- 
duces in the fields will be in the opposite direction. 

The magnetism, the fields, and all parts of the 



ELECTRICITY FOR ENGINEERS OO 

dynamo may be in perfect working order and yet a 
short circuit in any part of the wiring will prevent 
the dynamo from building up This short circuit 
will furnish a path of such low resistance that all cur- 
rent will flow through it and none can flow through the 
fields to induce magnetism. Often dynamos fail to 
generate because of broken wires in the field coils, 
poor contacts at brushes, or loose connections. Some- 
times also part of the wiring may be grounded on 
the metal parts of the dynamo frame. A faulty posi- 
tion of the brushes may also be a cause for the machine 
not generating. In some machines the proper position 
for the brushes is opposite the space between the pole 
pieces, while in other machines their proper position is 
about opposite the middle of the pole piece. If the 
exact position is not known, a movement of the brushes 
will sometimes cause the generator to build up. 

If there are several dynamos to be started great care 
must be taken to see that the second machine is oper- 
ating at full voltage before the switch is closed con- 
necting it to the switch board. The voltage should be 
exactly the same as that of the first machine and the 
rheoftat worked to keep it so. If it is less, it is pos- 
sib)e that the first machine will run the second as a 
motoi; if it is more, the second machine may run the 
first as motor, the machine having the higher voltage 
will always supply the most current. 

It is also necessary before throwing in the second 
machine (connecting it to the switch board) to see that 
its polarity is the same as that of the machine with 
which it is to run. By reference to Fig. 38 it will be 
seen that the + poles of both machines connect to the 
same b \r, and if one of these machines is running and 
we wisl to connect the other with it, we must first be 



i 



70 ELECTRICITY FOR ENGINEERS 

sure *hat the wire of the second machine which leads 
to tlie top bus-bar is of the same polarit3^ That is, if 
the top bus-bar is positive, or sends out current, the 
wire of all dynamos connected to it must also be posi- 
tive. 7'he simplest way to find the positive pole of a 
dynamo is with a cup of water. Take two small wires 
and connect one to each of the main wires of the 
dynamo and then insert the bare ends of both wires 
into the water, small bubbles will soon be seen to rise 
in the water from one of the wires. That wire which 
gives off the bubbles is the negative wire. Take care 
that in making this test you do not get the ends of the 
small wires together or against the metal of the cup or 
you will form a short circuit. The polarity of both 
dynamos must be tested and wires of same polarity 
connected to the same bus-bar. 

Where several machines are to be operated in paral- 
lel, compound dynamos are generally used, because it 
is troublesome to keep two shunt machines working in 
harmony. 

The starting of a compound wound dynamo is the 
same as that of a plain shunt dynamo, but in connect- 
ing a compound wound dynam^o to its circuit it is 
necessary to be sure that the shunt coils and series coils 
tend to drive the lines of force around the magnetic cir- 
cuit in the same direction. If the series coil is con- 
nected up in the opposite direction to the shunt coil 
the dynamo will build up all right and will work satis- 
factorily on very light loads. When, however, the 
load becomes even, five or ten per cent, of full load, 
the voltage drops off very rapidly and it is impossible 
to get full voltage with even half the load on. This is 
because the ampere turns due to the series coils 
decrease the total ampere turns acting on the magnetic 



ELECTRICITY FOR ENGINEERS 



71 



circuit instead of increasing them as the load comes 
on. This lowers the magnetic flux and of course 
lowers the resulting voltage. In such a case it will be 
necessary to reverse either the field or series coils. 

Fig. 38 and the following description of compound 
dynamos and their connections is taken from Wiring 
Diagrams and Descriptions^ by Horstmann and Tousley, 
published by Frederick J. Drake & Co., Chicago. 




FIGURE 38, 



Fig. 38 shows connections for two compound wound 
dynamos run in parallel. When two or more com- 
pound wound dynamos are to be run together, the 
series fields of all the machines are connected together 
in parallel by means of wire leads or bus-bars which 
connect together the brushes from which the series 
fields are taken. This is known as the equalizer, and 
is shown by the line running to the middle pole of the 
dynamo switch. By tracing out the series circuits it 



72 ELECTRICITY FOR ENGINEERS 

will be seen that the current from the upper brush of 
either dynamo has two paths to its bus-bar. One of 
these leads through its own fields, and the other, by 
means of the equalizer bar, through the fields of the 
other dynamo. So long as both machines are gener- 
ating equally there is no difference of potential between 
the brushes of No. i and No. 2. Should, from any 
cause, the voltage of one machine be lowered, current 
from the other machine would begin to flow through 
its fields and thereby raise the voltage, at the same 
time reducing its own until both are again equal. The 
equalizer may never be called upon to carry much cur- 
rent, but to have the machines regulate closely it 
should be of very low resistance. It may also be run 
as shown by the dotted lines, but this will leave all 
the machines alive when any one is generating. The 
ammeters should be connected as shown. If they 
were on the other side they would come under the 
influence of the equalizing current and would indicate 
wrong, either too high or too low. The equalizer 
should be closed at the same time, or preferably a lit- 
tle before the mains are closed. In some cases the 
middle, or equalizer, blade of the dynamo switch is 
made longer than the outside to accomplish this. The 
series fields are often regulated by a shunt of variable 
resistance. To insure the best results compound ma- 
chines should be run at just the proper speed, other- 
wise the proportions between the shunt and series coils 
are disturbed. 

GENERAL RULES 

1. Be sure that the speed of the dynamo is right. 

2. Be sure that all the belts are sufficiently tight. 

3. Be sure that all connections are firm and make good contact, 

4. Keep every part of the machine and dynamo room scrupu- 
lously clean. 



ELECTRICITY FOR ENGINEERS 73 

5. Keep all the insulations free from metal dust or gritty sub- 
stances. 

6. Do not allow the insulation of the circuit to become impaired 
in any way. 

7. Keep all bearings of the machine well oiled. 

8. Keep the brushes properly set and see to it that they do not 
cut or scratch the commutator. 

9. If the brushes spark, locate the trouble and rectify it at once. 

10. The durability of the commutator and brushes depends on 
the care exercised by the person in charge of the dynamos. 

11. At intervals the viynamos must be disconnected from the 
circuit and thoroughly tested for leakage and grounds. 

12. In stations running less than twenty-four hours per day, the 
circuit should be thoroughly tested and grounds removed (if any 
are found) before current is turned on. 

13. Before throwing dynamos in circuit with others running in 
multiple, be sure the pressure is the same as that of the circuit ; 
then close the switch. 

14. Be sure each dynamo in circuit is so regulated as to have its 
full share of load, and keep it so by use of resistance box. 

15. Keep belting in good order; when several machines are 
operating in parallel and a belt runs off from one, the others will 
run this machine as a motor. 

16. In the same way if you shut down an engine driving a 
generator, the other generators will run the generator and the 
engine. 

Constant Potential Switchboard. In Fig. 39 we show 
the usual type of switchboard employed to connect, 
or switch various dynamos and to feed various circuits 
from. These types, sizes and arrangements of switch- 
boards vary and depend entirely on the type and size 
of the plant, the number of dynamos used and the num- 
ber of circuits to be controlled. The switchboard in 
this cut has three dynamo panels and one load panel. 
At the left of the board and near the top is the volt- 
meter, while on the three left panels are the dynamo 
main switches and their respective amperemeters. On 
the lower part of these three machine paneU will be 



74 



ELECTRICITY FOR ENGINEERS 



noticed the protruding hand wheels of the field resist- 
ance boxes, which are hidden back of the board. The 
meter at the top of the right hand panel is the load 
amperemeter and registers the total number of amperes 




FIGURE 39. 



that are being supplied to the circuits whose several 
switches are just below the meter. 

Fig. 40 shows diagrammatically the reverse side of a 
similar switchboard. Below all of the switches there 
are installed fuses in each wire. The object of these 
fuses is to protect the wires and also the dynamos. 
These fuses consist of av alloy which melts at a com- 



ELECTRICITY FOR ENGINEERS 



75 



paratively low temperature. If, for instance, a short 
circuit occurs in any line, the current will suddenly 
become very great and will generate considerable heat. 
This heat will cause the fuse to melt and open the cir- 
cuit. If tlie fuse did not melt the current would con- 
tinue and overheat the wires, causing considerable 






+i 



Egualili; 



"^ I 






6 6 6 
"T" 9 9 Q 



ev 



6 6 6 
+9 9 9 



6 6 6 
+ 9 9 9 






.■¥ 



/ ^ - 66 66 66 66 

?§ n ti n 

<^y '^? y y _ 



6 (J 



1X2+ \%% + 



mill 

Su>\tche6 



FIGURE 40. 



damage and perhaps fires. The fuses should always 
be chosen of such a size that they will melt before the 
current rises enough to do any damage. 

Operation of Constant Current Dynamos. Constant cur- 
rent dynamos differ from constant potential dynamos 
mainly in the higher voltage for which they are usuahy 



76 ELECTRICITY FOR ENGINEERS 

constructed. Such machines are always more or I'tss 
dangerous to life, and great care must be taken not to 
touch any of the current-carrying parts with bare hands. 

When such parts must be handled rubber gloves are 
very convenient and useful if kept dry. High voltage 
machines should always be surrounded by insulating 
platforms of dry wood, or rubber mats, so arranged 
that one must stand on them in order to touch any 
part of the machine. By reference to Fig. 19 it will 
be seen that the constant current dynamo is not 
equipped either with a voltmeter or a field rheostat; 
but an amperemeter should always be used. The 
troubles encountered with these dynamos are much the 
same as those of constant potential dynamos. Most of 
them are referred to in the following descriptions and 
instructions for different systems and to avoid repeti- 
tion need not be mentioned here. 

The type of dynamo generally used with constant 
currents is shown in Fig. 19 and is series wound; that 
is, the same current that passes through the lights also 
passes through the fields and excites them^. The fields 
of this dynamo are connected with a short circuiting 
switch, S, which is generally used when the machine is 
to be shut down. When this switch is closed it forms 
a path of much lower resistance than do the fields of 
the dynamo and all current passing through it and the 
dynamo loses its magnetism and stops generating. 
A constant potential dynamo will not begin genera- 
ting if there is a short circuit anywhere in the wiring 
connected with it, but with the constant current 
dynamo it is often necessary to provide a short circuit 
in order to start it. If there is very much resistance 
in the line or if H is entirely open the dynamo will fail 
to generate. 



ELECTRICITY FOR ENGINEERS 77 

In order to start generation a small wire may be 
attached to one of the terminals of the dynamo and 
the other end brought in contact with the other ter- 
minal for a fraction of a second or the shortest possible 
instant. If the circuit happens to be arranged some- 
what as shown in the figure, the plug may be inserted 
so that the dynamo is started through only one lamp. 
When this lamp is burning properly the plugs may be 
suddenly withdrawn and the current will now force 
itself through the other lamps. This process is known 
as ''jumping in'' and should be used only in an emer- 
gency, as much damage may be caused, especially if a 
dynamo is already running a large number of lamps 
and is then "jumped into" a bad circuit. This is also 
often done, but is just as dangerous as it would be to 
attempt to start a heavy steam engine by opening up 
the throttle valve with a quick jerk. 

Constant current dynamos are always equipped with 
automatic regulators and before the dynamo is started 
special attention must be given the regulator to see 
that it is in proper working order. 

Often it may be desirable and even necessary to run 
two dynamos in series, as, for instance, if a circuit has 
been extended beyond the capacity of one machine. 
In such a case the regulator of one machine is cut out 
and that machine set to operate at about its highest 
electromotive force, and the variations are taken care 
of by the other dynamo. 

The Brush System. The brush arc dynamo is quite 
distinct from other constant current dynamos in general 
use. We shall therefore give the following descrip- 
tion of it taken from literature furnished by the Gen- 
eral Electric Company. 

The brush arc generator is of the open coil type, the 



78 ELECTRICITY FOR ENGINEERS 

fundamental principle of which is illustrated in Fig. 
41. Two pairs of coils, placed at right angles on an 
iron core, are rotated in a magnetic field. The hori- 
zontal coils represented in the diagram are producing 
their maximum electromotive force, while the pair of 
coils at right angles to them is generating practically 
no electromotive force. The brushes are placed on 
the segments of the four-part commutator, so as to col- 
lect only the current generated by the two horizontal 




FIGURE 41. 

coils. The other coils are open circuited or com- 
pletely cut out of the circuit. 

Such a machine will generate current, continuous in 
direction, but fluctuating considerably in amount. 
These fluctuations will be diminished by the addition 
of more coils to the armature. 

Fig. 42 shows the connections of an eight-coil brush 
arc generator. Each bobbin is connected in series 
with the one diametrically opposite. The connection 
is not shown on the diagram. It will be noticed that 
of those coils connected to the outer ring on which the 
brushes A and A^ bear, only 3, 3^ are in circuit, I, i^ 



ELECTRICITY FOR ENGINEERS 



79 



being entirely cut out; while on the inside ring all 
coils 2, 2^ and 4, 4^ are in circuit, the two pairs being 
parallel; 4, 4^ are coming into the field of best action; 
in other words, they are approaching that part of the 
field in which there is most rapid change of magnetic 
flux, while 2, 2^ are approaching that part in which the 
flux is uniform. In 4, 4^ there is an increasing electro- 




FIGURE 42. 

motive force being generated, and the current is rising; 
while in 2, 2\ the electromotive force is decreasing and 
the current falling. Unless 2, 2^ were cut out of the 
circuit, a point would soon be reached where the elec- 
tromotive force in 2, 2^ would be zero, and conse- 
quently 4, 4^ would be short circuited through 2, 2^ 
Just before this occurs, however, 2, 2^ have passed from 
under the brush and the small current still flowing 



80 ELECTRICITY FOR ENGINEERS 

draws out the spar^ one sees on the commutator of all 
open coil machines. 

Setting the Brushes. A pressure brush should always 
be used over the under brush in the'same holder, as it 
improves the running of the commutator and secures 
better contact on the segment. The combination is 
referred to as the "brush." The brushes should be 
set about $}i in. from the front side of the brass brush« 
holder. 

^n setting the brushes, commence with the inner pa " 
and set one brush about 5^ in. from the holder to tip 
of the brush, then rotate the rocker or armature unti*. 




FIGURE 43. 

the tip of the brush is exactly in line with the end of a 
copper segment, as shown in Fig. 43. The other 
brush should be set on the corresponding segment 90° 
removed (the same relative position on the next for- 
ward segment); but if the length of the brush from the 
holder is less than 5^ in., move both brushes forward 
until the length of the shorter brush from the holder 
is 5^ in. Now set the two extreme outer brushes in 
the same manner, clamping firmly in position, and b}' 
using a straight edge or steel rule, all the brushes can 
be set in exactly the same line and firmly secured. 
The spark on one of the six brushes may be a trifle 



ELECTRICITY FOR ENGINEERS SI 

longer than on the others. In this case, move the 
brush forward a trifle so as to make the sparks on the 
six brushes about the same length. Equality in 
the spark lengths is not essential, but it gives at a 
glance an indication of the running condition of the 
machine. 

Brushes should not bear on the commutator less than 
}i in. from the point of the brush, or, as illustrated in 
Fig. 44 (a), they will tend to drop into the commu- 
tator slots and pound the copper tip of the wood block, 
causing the fingers of the brushes to break off. If, on 
the other hand, the bearing is too far from the end, or 
the brushes are set too long, as in Fig. 44 (b), the 



I i ^ I 

FIGURE 44a. figure 44b. figure 44c. 



point of the brush will not bq in contact with the seg- 
ment, thereby prolonging the break, and allowing the 
spark to follow the tip with consequent burning of the 
segments and brushes. 

Fig. 44 (c) shows correct seating with the tip of the 
brush nearly tangential and stiff on the segment as it 
leaves. 

Care of Commutator. If the commutator needs lub- 
rication, oil it very sparingly. Once or twice during 
a run is ample. If the oil has a tendency to blacken 
the commutator instead of making it bright, wipe the 
commutator with a dry cloth. Too much oil causes 
flashing. 

The machine, of course, generates high potential, 
and the cloth, or whatever is used to oil the commu- 



82 ELECTRICITY FOR ENGINEERS 

tator, should therefore be placed on a stick so thai the 
hand is not placed in any way between the brushes. 

A rubber mat should be provided for the attendant 
to stand on when working around the commutator or 
brushes. 

One hand only should be used, and great care exer- 
cised not to touch two brush clamps or brushes at the 
same time; never with switches closed. 

As soon as current is shut off from the machine the 
commutator should be cleaned. A piece of very fine 
sandpaper held against the commutator under a strip 
of wood for about a minute before the machine is 
stopped, will scour the commutator sufficiently. The 
brushes need not be removed. An effort should be 
made to have the machine cleaned immediately after 
it is shut down. Five minutes at that time will give 
better results than half an hour when the machine is 
cold. Never use a file, emery cloth or crocus, on the 
commutator. New blocks will sometimes cause flash- 
ing, due to the presence of sap in the wood. The 
machine should be run for a few hours with a slightly- 
longer spark, say Yz in., and the commutator then 
thoroughly cleaned with fine sandpaper. 

All constant current arc machines require an auto- 
matic regulator to increase the voltage as more lamps 
are cut into the circuit and decrease it as lamps are 
cut out. 

We will give only one of the several forms of regu- 
lators used with this system. 

The form i regulator is placed on the frame of the 
machine beneath the commutator, and a constant 
motion is imparted to its main shaft through a small 
belt running around the armature shaft. (See Fig. 
46.) By means of magnetic clutches and bevel gears, 



ELECTRICITY FOR ENGINEERS 



8S 



a pinion shaft is rotated, which moves the rack and the 
rocker arm and so shifts the brushes on the commu- 
tator to maintain a spark of about ^ in. on short cir- 




^ Controller 



\ To Controller 



FIGURE 46. 



,5Uit and }i in. at full load; at the same time th> 
rheostat arm is moved over the contacts to cut 
resistance in or out of the shunt around the field 
circuit. 



84 



ELECTRICITY FOR ENGINEERS 



The current for the magnetic clutches is regulated by 
the controller. 

The controller consists principally of two magnets 
which are energized by the main current and act when 
the current is too high or too low by sending a small 
current to one of the clutches. 

A careful examination of the controller (see Fig. 
47), in connection with Fig. 46, will give a clear idea 



GONNECTIONS OF BRUSH GONTROLLER 



/^To Circuit or ^mjneler 




To Clu-tch s-b F for- Clockwise. 

To Clu-tch at E for Counter Clockwise. 



To Clutch at E for Clockwise. 

To Clutch at F for Counter Clockwise 



Changed 6 June '98. 



FIGURE 47. 



of its regulating action. It is generally advantageous 
to make the yoke which carries the brushes on the 
machine and the arm moving the rheostat, rather 
tight. As the magnetic clutches act with considerable 
force, it is not necessary to adjust these moving parts 
so loosely that they will move without considerable 
pressure on the rocker handle. Less difficulty will 
then be experienced in adjusting the controller. 



ELECTRICITY FOR ENGINEERS 85 

For shunt lamps, the controller may be adjusted to 
permit a variation of .4 ampere above or below normal; 
for differential lamps, the variation above and below 
normal should not exceed .2 ampere. The limits 
given in the following instructions are for differential 
lamps, and may be extended .2 ampere above or below 
for shunt lamps. 

If the controller is out of adjustment and fails to 
keep the current normal, do not try to adjust the ten- 
ions of both armatures at the same time. For exam- 
ple, suppose the current is too high, either one of the 
two spools may be out of adjustment. The left-hand 
spool I may not take hold quickly enoLigh, or the 
spool F may take hold too quickly. To make the 
adjustment, screw up the adjusting button K on the 
right hand spool, increasing the tension. This will 
have a tendency to let the current fall much lower 
before the armature comes in contact with H, to cause 
the current to increase. By simply tapping the arma- 
ture G quickly with a pencil or piece of wood, forcing 
it down to its contact, and at the same time watching 
the ammeter, the current may' be brought up to 6.8 
amperes if 6.6 amperes is normal, or to 9.8 if 9.6 
amperes is normal. With the current at 6.8 amperes, 
which is .2 ampere high, the adjusting button L should 
be turned to increase the tension on this spring until 
the armature M comes in contact with contact N, 
which will force current down through O. The clutch 
which pulls the brushes forward and rocks the rheostat 
back for less current will thus be energized. Repeat 
this adjustment two or three times, but do not touch 
the adjusting button K; adjust L until it is just right. 

At the side of the armature M a little wedge is 
screwed in by means of an adjusting button, and 



86 ELECTRICITY FOR ENGINEERS 

increases or decreases the leverage on this armature. 
See that this wedge is fairly well in between the core 
or frame of the spool and the spring of the armature. 
The armature M may have to be taken out and the 
spring slightly bent. It is advisable to have the screw 
which passes through the adjuster button L about half 
v/ay in, to allow an equal distance up and down for 
adjusting this lighter spring after the wedge shaped 
piece is in the right position to give the necessary 
tension on the spring which is fastened to the arma- 
ture M. 

In the right-hand corner P, a small bent piece of 
wire is placed for tightening up the screw which fas- 
tens the spring to the frame of the spool. As the con- 
tact made by the spring and the frame of the spool 
held together by a screw and button is a part of the 
magnetic circuit, it will be almost impossible to get 
this spring back to exactly the same tension after once 
removing it. Therefore, the adjusting buttons of the 
controller must be turned slightly in order to bring it 
back to its proper adjustment. This, however, is an 
after consideration, and care should be taken to have 
the screw which holds the spring and frame together 
always tight. 

Having adjusted the spool I so that the current will 
not rise above 6.8 amperes (or 9.8 amperes), move the 
armature M up to contact N with a pencil or piece of 
wood, causing the current to be reduced to about 6.2 
(or 9.2). After the current settles at this point, decrease 
the tension on the spring which is fastened to armature 
G, allowing this armature to fall down to contact H. 
Current will then flow through Q, which will rock the 
brushes back and also move the rheostat arm for more 
current. As the spool I has been adjusted for 6.8 (or 



ELECTRICITY FOR ENGINEERS 87 

9.8) amperes, the current cannot rise above that amount 
no matter how the spool F is adjusted. 

With very little practice in moving the armature of 
one spool with a pencil, the other can be adjusted 
much more readily than if an attempt is made to adjust 
the screws K and L at the same time. 

The two small shunt coils, R and S, are connected 
around the two contacts simply to decrease the spark 
between the silver and platinum contacts. If they 
should become short circuited in any way, so that 
their resistances become diminished, sufficient current 
may pass through either of them to operate the regu- 
lator. If unable to locate the trouble disconnect these 
coils at points T and U, when a thorough examination 
can be made. M and G need not move more than just 
enough to open the contact; -^^ in. is ample. 

In starting the machine, the lower switch, which 
short circuits the field, should be opened last. 

The switch in the left-hand corner of the controller, 
figure 47 cuts out the two resistance wires which are 
used to force the current through wires O and Q to 
the clutches. Open this switch, which leaves the 
automatic device of the controller in circuit, so that it 
will move the brush rocker. Unclamp the brush rocker 
from the rheostat arm rocker. Move the brushes by 
hand to give the proper spark, allowing the rheostat 
arm, however, to be moved by the controller. After 
the switches are opened, the rheostat arm will go clear 
around to a full load position, and then, as the current 
rises, the controller takes hold and brings the arm 
back. In the meantime, rock the brushes forward c( 
backward and keep the spark about the proper length, 
say }i in., at full load to ^ in., on short circuit. 
Gradually the rheostat arm will settle, the spark will 



88 ELECTRICITY EOR ENGINEERS 

become constant, and the machine will give its proper 
current. Then clamp the rocker and rheostat arm together 
and let the machine regulate itself. 

This method is much better than opening the 
switches on the machine and allowing the wall con- 
troller to take care of the machine from the start. By 
allowing the controller to start the machine, a trifle 
longer spark is obtained than by the other m,ethod, 



COMMUTATOR END 




FIGURE 48. 



unless the machine is run from the beginning on a very- 
full load. 

The machine will require a trifle longer spark on light 
load, or on bad circuits, than when running at full load. 
This fact should be borne in mind in wet weather, when 
trouble with grounds is experienced. 

A reliable ammeter should always be connected in 
the circuit of an arc generator, so that the exact cur- 
rent may be read at a glance. It should be connected 
into the negative side of the line where the circuit leaves 
the regulator. 



ELECTRICITY FOR ENGINEERS 



The Thomson-Houston System. The Thomson-Hous- 
ton dynamo differs from other arc dynamos principally 
in the nature of its armature winding. This is shown 
in Fig. 48. One end of each of the three coils is con- 
nected to a copper ring common to all. The other end 
of each coil terminates at one of the three commutator 
segments. The management and operation of the 
machine will appear from the following instructions 
taken from pamphlets furnished by the General Elec- 
tric Company. 




FIGURE 50. 

Setting the Cut-out. After the brushes are in position 
the cut-out must be set. This is done by turning the 
commutator on the shaft in the direction of rotation 
(if the commutator is set in position the whole arma- 
ture must be revolved) until any two segments are just 
touching the primary brush on that side, as segments A' 
and A'" touch brush B* in Fig. 50. 

Under these conditions brush B^ should be at the 
left-hand edge of upper segment. Then turn commu- 
tator until the same two segments are just touching 



90 ELECTRICITY FOR ENGINEERS 

brush B^, when the end of brush B^ should just come 
to the right-hand edge of the lower segment. If the 
secondary brush projects beyond the edge of the seg- 
ment the regulator arm should be bent down; if it does 
not come to the edge of the segment, the arm should 
be bent up. 

Care must be taken that the regulator armature is 
down on the stop when the cut-out is being set. 
These adjustments by bending regulator arm are 
always made in the factory before testing the machine, 
and should never be made on machines away from the 
factory, unless the regulator arm has been bent by 
accident. If it becomes necessary to make any adjust- 
ments they should be made by means of the sliding 
connection attached to the inner yoke. 

Always try the cut-out on both primary brushes. If 
it does not come the same on both, turn one over. If 
the brush-holders are correctly set by the gauge, there 
should be no trouble in getting the cut-out set properly 
after one or two trials. 

To set the commutator in the proper position on a 
right-hand machine, with a ring armature, find the 
leading wire of No. I coil. It is the custom in the 
factory to paint this lead red, also to paint a red mark 
on the center band between two groups of coils, 
namely, the last half of No. i coil and the first half of 
No. 3 coil. The first half of a coil is that group from 
which the lead comes. The last half is diametrically 
opposite the first half and the lead wire belonging to 
it is connected with the brass ring on the outside of 
the connection disk on the commutator end. 

In Fig. 51 the first halves of the three coils are rep- 
resented by I, 2 and 3, and the last halves by l', 2' 
and 3\ 



ELECTRICITY FOR ENGINEERS 



91 



A narrow piece of tin with sharply pointed ends is 
t?ent up over the sides of the middle band at the cen- 
ter of the red mark so that the points are opposite each 
other. 

When the red mark and red lead have been found, 
turn the armature until the last half of No. i coil has 
wholly disappeared under the left field and until the 
left-hand edge of the first coil to the right of the red 







FIGURE 51. 



mark (No. 3 in Fig. 51) is just in line with the -dge of 
the left field. The red lead will then be in position 
shown in Fig 51, and the armature is in proper posi- 
tion to set the commutator. 

In the case of the right-hand drum armature »he 
leading wire of the first coil should be found. This 'ead 
maybejecognized from the fact that it is more heavily 
insulated than the rest, and is found in the center of 



ELECTRICITY FOR ENGINEERS 




FIGURE 52. 



the outer coil, on the commutator end. With this 
mre turned underneath, rotate the armature forward^ 
or counter-clockwise, until the pegs on the right-hand 




Red marK paiin'Ceud 



FIGURE 5-^. 



ELECTRICITY FOR ENGINEERS 



9S 



side of this coil just disappear under the left field. 
(See Fig 52.) 

The position of the red lead and the red mark on the 
band are the same on all armatures, but their positions 
in the fields of the machines called left-hand (clock- 
wise rotation), should be as shown in Fig. 53 and 54 
when setting the commutator. 

When the armature of a right-hand machine is in 
position, the commutator is turned on the shaft until 




FIGURE 54. 



segment No. i is in the same relative position as the 
last half of No. i coil; segment No. 2 should corres- 
pond with the last half of No. 2 coil, and segment No. 
3 with the last half of No. 3 coil, as shown on Figs. 51 
and 52. 

For left-hand machines, see Figs. 53 and 54. 

The distance from the tip of the brush, which is on 
top, to the left-hand edge of No. 2 segment on a right- 
hand machine, or to the right-hand edge of No. 3 seg- 



94 ELECTRICITY FOR ENGINEERS 

ment in a left-hand machine is called the lead, and 
should be made to correspond with the following 
table. 





TABLE 


OF 


LEADS 




DRUM ARMATURES. 




RING ARMATURES. 


C12 i inch 


positive 




K12 A inch positive 


C2 f - 






K^ i - 


i <( 


eiVt - 






M12 ^ - 


' negative 


E2 ^ «' 






M2 1 " 


1 (( 


H12 1 a 






LD12 J " 


' positive 


H^ i - 






LD2 1 '' 
MDi2^| ' 
MD2 13 * 


«i 



Place the screws in the binding posts at the lower 
ends of the sliding connections, and put on the dash 
pot connections between the brushes, with the heads 
of the connecting screws outward. In every case the 
barrel part of the dash pot is connected to the top 
brush-holder, and plunger part to the bottom brush- 
holder. 

See that the field and regulator wires are connected 
and that all connections are securely made. 

When all connections have been made, make a care- 
ful examination of screws, joints and all moving parts. 
They must be free from stickiness and not bind in any 
position. 

To determine when the machine is under full load, 
notice the position of the regulator armature, which 
should be within }i in. of the stop. At full load the 
normal length of the spark on the commutator should 
be about y\ in. If it is less than this, shut down the 
machine and move the commutator forward or in the 
direction of rotation until the spark is of the desired 
length. If the spark is too long, move the commu- 
tator back the proper amount. 

A general view of the complete dynamo is given id 



ELECTRICITY FOR ENGINEERS 



95 



Fig. 55, and will help explain the regulator used with 
this system. 

The regulator is fastened to the frame of the machine 
by two short bolts. On the right-hand machine its 
position is on the left-hand side, as shown in Fig. 55. 
On the left-hand machine, i.e,^ one which runs clock- 
wise, its position is on the opposite side. Before fill- 




FIGURE 55. 



ing the dash pot D with glycer.ne, see that the 
regulator lever and its connections, brush yokes, etc., 
are free in every joint, and that the lever L can move 
freely up and down. Then fill the dash pot D with 
<;oncentrated glycerine. The long wire from the 
regulator magnet M is connected with the left-hand 
iiQding post P of the machine, and the short wire with 



96 ELECTRICITY FOR ENGINEERS 

the post P^ on the side of the machine. The inside 
wire of the field magnet, or that leaving the iron flange, 
of the left-hand field should be connected into post P^ 
also, as shown in Fig. 55. The electric circuit (see 
Fig. 56) should be complete from post P\ on the con- 
troller magnet, through the lamps to the post N 01a the 
machine, through the right-hand field magnet C, to 
the brushes B^B^ through the commutator and arma- 
ture to the brushes B B, through the left-hand field C, 




FIGURE 56. 



to posts P^ and P, thence to posts P^ and P on the con- 
troller magnet, through the controller magnet to P^ 
'^^TSie current passes in the direction indicated by the 
arrows 

When an arc machine is to be run frequently at a 
small fraction of its normal capacity, the use of a light 
load device is advisable to secure the best results in 
regulation. 

The rheostat for this purpose (see Fig. 57) is con- 
nected in shunt with the right field of the generator. 



ELECTRICITY FOR ENGINEERS 



97 



Facing the rheostat with the right binding posts at the 
bottom, the contact on the right side or No. *i gives 
open circuit and throws the rheostat out of use. Point 
No. 2 gives a resistance of 44 to 46 ohms and Point 
No. 3 gives a resistance of 20 to 22 ohms. 

This rheostat with a 75-light machine allows the fol- 
lowing variations: Point I, 75 to 48 lights; Point 2, 
48 to 25 lights; Point 3, 25 lights or less. For use with 




FIGURE 57. 



other sizes of generators, the adjustment of the rheo^ 
Stat must be made to suit the conditions. 

When the rheostat is in use, the sparks at the com- 
mutator will be somewhat larger than normal, but will 
not be detrimental. 

The controller magnet (see Fig. 58) is to be fastened 
securely by screws to the wall or some rigid upright 
support, taking care to have it perfectly plumb. It is 
connected to the machine in the manner shown in Fig. 
55, i.e.^ the binding post P^ on the controller magnet is 



98 ELECTRICITY FOR ENGINEERS 

connected to the binding post P^ (see Fig. 55) on the 
end of the machine, and likewise the post P on the 
controller to the post P on the leg of the machine; 
the post P^ forms the positive terminal from which the 
; ircuit is run to the lamps and back to N. 

Great care should be taken to see that the wires P P 




FIGURE 58. 



and P^ P^ are fastened securely in place; for if connec- 
tion between P and P should be impaired or broken, 
the regulator magnet M would be thrown out of action, 
thus throwing on the full power of the machine, and if 
the wire P^ P^ should become loosened, the full power 
of the magnet M would be thrown on, and the regu- 



ELECTRICITY FOR ENGINEERS 99 

lator lever L, rising in consequence, would greatly 
weaken or put out the lights. 

The wires leading from the controller magnet to the 
machine should have an extra heavy insulation. 

Care should be taken in putting up the controller 
magnet that the following directions are followed: 

1. The cores B of the axial magnets C C must hang 
exactly in the center, and be free to move up and 
down. 

2. The screws fastening the yoke or tie pieces to the 
two cores must not be loosened. 

3. The contacts O must be firmly closed when the 
cores are not attracted by the coils C C, which is the 
case, of course, when no current is being generated by 
the machine, and when the cores are lifted, the con- 
tacts must open from ^^j in. to ^^ i^^- > ^ greater open- 
ing than ^^^ in. has the effect of lengthening the time 
of action of the regulator magnet. This tends to ren- 
der the current unsteady, and in case of a very weak 
dash pot or short circuit might cause flashing. Adjust- 
ment must be made if necessary by bending the lower 
contact up or down, taking care that it is kept parallel 
with the upper contact, so that when they are closed, 
contact will be made across its whole width. If this 
adjustment is not properly made there will be destruc- 
tive sparking on a small portion of the contact surfaces. 

4. All connections must be perfectly secure. 

5. The check nuts N must be tight. 

6. The carbons in the tubes L must be whole. These 
carbons form a permanent shunt of high resistance 
around the regulator magnet M, and if broken will 
cause destructive sparking at contacts O, burning them 
and seriously interfering with close regulation of the 
generator. In case a carbon should become broken, 



100 



ELECTRICITY FOR ENGINEERS 



temporary repairs may be made by splicing the broken 
pieces with a fine copper wire. 

To keep the action of the controller perfect the con- 
tacts O should be occasionally cleaned by inserting a 
folded piece of fine emery cloth and drawing it back 
and forth. 

The amount of current generated by each machine 



S^HHl 




FIGURE 59. 



depends upon the adjustment of the spring S. If the 
tension of this spring is increased the current will be 
diminished; if the tension is diminished, the current 
will be increased. 

In starting these dynamos when the armature has 
reached its proper .speed, the short circuiting switch on 
the frame should be opened. This method allows the 



ELECTRICITY FOR ENGINEERS 



101 



generator to take up its load gradually, and Is a very 
important point in the handling of the machine. 

Arc Switchboards. Fig. 59 shows a general view of 
the Thomson-Houston plug switchboard. A rear view 
of the same board is given in Fig. 60. 

In a standard panel the number of horizontal rows 
of holes equals one more than the number of gener- 
ators. The vertical holes are always twice the number 
of generators. The positive leads of the generators are 




FIGURE 60. 



attached to the binding posts on the left-hand ends of 
the horizontal conductors. The negative leads are 
connected to the corresponding binding posts at the 
right-hand end of the board. 

The positive line wires are connected to the vertical 
straps on the left, and the negative wires to the similar 
straps on the right of the center panel. 

If a switchboard plug be inserted in any of the holes 
of the board, it puts the corresponding generator lead 



102 ELECTRICITY FOR ENGINEERS 

and the line wire in electrical connection, but as the 
positive line wires are back of the positive generator 
leads only, it is not possible to reverse the connection 
of the line and the generator accidentally, though any 
other combinations of lines and generators can be 
maae readily and quickly. 

The holes of the lower horizontal rows have bushings 
connected with the vertical straps only. Plugs con- 
nected in pairs by flexible cable and inserted in the 
holes put the corresponding vertical straps in connec- 
tion as needed, and normally independent lines maybe 
connected when one generator is required to supply 
several circuits. 

Lines and generator leads may be transferred, while 
running, by the use of these cables, without shutting 
down machines or extinguishing lamps. 

The standard boards are arranged for an equal num- 
ber of generators and circuits, but special boards for 
any ratio of circuits to generators can be built. 

As it is sometimes convenient, even in small plants, 
to interchange lines and generators without shutting 
down machines, a special transfer cable with plugs has 
been devised. This serves the same purpose as the 
regular transfer cable, but the plugs may be used in 
any of the holes of the switchboard, as they are insu- 
lated, except at the tip, and when inserted connect 
with the line strips only. 

The transfer of circuits from one generator to 
another gives trouble to dynamo tenders who are not 
familiar with the operation of these plug switchboards. 
Fig. 6i illustrates the successive steps for transferring 
the lamps of two independent circuits from two genera- 
tors to one without extinguishing the lamps on either 
circuit. 



ELECTRICITY FOR ENGINEERS 



lOS 



() 



o o 
o o 



o o 

o o 

o o 

o o 



■n 



Tt 



o o o o 
o o o o 











B 














' 


ih * 


» o 


o 


"i 


h- 


^ 


r\ 


C\ 




1 


\ > 




\J 


KJ 


1 1 




i k. 


1 


\ o 


o 


o 


i 


r\ 


r^ 


1 


2 


V 


^ 


• 


CJ 


\J 


2 


3 


o 


c 


) o 


o 


o 


o 


o 


o 


3 




o_ 


_c 


) o 


o 


o 


o 


o 


o 















c 


















r 


d 


k 


o 
o 


o 
o 


d 


. 


f 


r-\ 


/"V 






1 


o 


o 






1 


1 


2 


^ 


9— 


u 


CJ 


2 




3 


o 


o 


o 


o 


o 


o 


o 


o 


3 






o_ 


o 


o 


o 


o 


o 


o 


o 








FIGURE 61. 



104 ELECTRICITY FOR ENGINEERS 

This process is a very simple example of switch- 
board manipulation, but illustrates the method used 
for all combinations. 

The location of plugs is shown by the black circles, 
which indicate that the corresponding bars of the 
horizontal and vertical rows are connected. 

Circuit No. i and No. 2, running independently from 
generators No. i and No. 2 respectively, are to be 
transferred to run in series on generator No. 2. 

In A, Fig. 61, are two circuits running independently; 
in B the positive sides of both generators and circuits 
are connected by the insertion of additional plugs. 

At C both generators and circuits are in series. 

Next insert plugs and cables as shown in D. Then 
withdraw plugs on row corresponding to generator No. 
I, and the circuits No. i and No. 2 are in series on 
machine No. 2, and machine No. i is disconnected as 
at E. 

Similar transfers can be made between any two cir- 
cuits or machines, and by a continuation of the process 
additional circuits can be thrown in the same machine. 
The transfer of the two circuits to independent genera- 
tors is accomplished by reversing the process illus- 
trated. 

Fig. 62 shows the wiring and connections of the 
Western Electric Co.'s series arc switchboard. At the 
top of the board are mounted six ammeters, one being 
connected in the circuit of each machine. On the 
lower part of the board are a number of holes, under 
which, on the back of the board, are mounted spring 
jacks to which the circuit and machine terminals are 
connected. For making connections between dynamos 
and circuits, flexible cables terminating at each end in 
a plug, are used; these are commonly called '^jump* 



ELECTRICITY FOR ENGINEERS 



105 



ers." The board shown has a capacity of six machines 
and nine circuits^ and with the connections as shown 
machine I is furnishing current to circuit i, machine 2 
is furnishing current to circuits 2 and 3, and machine 4 
is furnishing current to circuits 4, 5 and 7. In con- 
necting together arc dynamos and circuits the positive 
of the machine (or that terminal from which the cur- 
rent is flowing) is connected to the positive of the cir- 




riGURE 62. 



cuit (the terminal into which the current is flowing). 
Likewise the negative of the machine is connected to 
the negative of the circuit. Where more than one cir- 
cuit is to be operated from one dynamo, the — of the 
first circuit is connected to the + of the second. At 
each side of the name plate (at 3, for instance) there 
^^^ "V^^. holes. The large hole is used for the per- 
manent connection, while the smaller holes are used 
for transferring circuits, without shutting down the 



±06 ELECTRICITY FOR ENGINEERS 

dynamo. Smaller cables and plugs are used for 
transferring. If it is desired to cut off circuit 5 from 
machine 4, a plug is inserted in one of the small holes 
at the right of 4, the other plug being inserted in one 
of the holes at the left of 7. Circuit 5 would now be 
short circuited, and the plug in the + of 5 can now be 
transferred to the permanent connection in the + of 7, 
and the cords running to 5 removed. If it is desired 
to cut in a circuit, say circuit 6 onto machine 2, insert a 
cord between the — of circuit 2 and the -h of 6 and an- 
other between the — of 6 and the + of 3. Now pull the 
plug on the cord connecting — of 2 and the + of 3 and 
insert the permanent connections. In cutting in cir- 
cuits, if they contain a great number of lights, a long 
arc may be drawn when the plug between 2 and 3 is 
pulled, and it is sometimes advisable to shut down the 
machine when making a change of this kind. 



CHAPTER V 

MOTORS. — ALTERNATING CURRENT MOTORS. 

Motors. Any dynamo may be used as a motor and con- 
sequently we have as many types of motors as there are 
types of dynamos. The pull of a motor depends upon 
the repulsion and attraction between the lines of force, 
or magnetism of the wire and core of the armature and 
that of the fields. We have seen that in a dynamo, as 
we force a wire through a magnetic field, current is 
generated. The more current there is generated or 
flowing in such a wire, the greater will be the expendi- 
ture of power necessary to force such a wire through a 
magnetic field; in other words, the currents flowing in 
the wires of a dynamo armature, always tend to drive 
the armature in a direction opposite to that in which it 
is being driven. 

If, then, instead of revolving a dynamo armature by 
mechanical means, we connect it to a source of elec- 
tricity and allow a current to flow through it we must 
obtain motion, and the direction of this motion will 
cfepend upon the direction in which the current flows, 
so long as this current does not alter the magnetism of 
the fields. 

We have already seen that the electric motor is built 
exactly like a dynamo; consequently, as its armature 
revolves it not only does useful work, such as turning 
whatever machinery it is belted to, but it also gener- 
ates an electromotive force. For instance, if a motor, 
running at full speed and receiving current from a 

107 



108 ELECTRICITY FOR ENGINEERS 

dynamo (Fig. 63), were suddenly disconnected by 
opening the main switch, it would at once begin acting 
as a generator and sending out current. This can be 
easily seen with any motor equipped with a starting 
box, such as shown; for the current from the motor 
will continue to energize the fields and the little mag- 
net M so as to hold the arm of the starting box until 
the motor has nearly come to rest. If it were not for 
the current generated by the motor, this arm would fly 
back the instant the switch is opened. 

The electromotive force set up by a motor always 
opposes that of the dynamo driving it; that is, the 
current which the motor tends to send out would flow 
in the opposite direction to that which is driving it. 

This may be compared, and is somewhat similar, to 
the back pressure of the water which a pump is forcing 
into a tank. If the check valves were removed and 
the steam pressure shut off, the water would tend to 
force the pump backward. 

This electromotive force is called the counter elec- 
tromotive force of the motor. The counter electro- 
motive force of the motor varies with the speed of the 
motor and also limits the speed of the motor, for it is 
obviously impossible that a motor should develop 
higher counter E. M. F. than the E. M. F. of the 
dynamo driving it. 

This highest possible speed of a motor is, then, that 
speed at which its counter E. M. F. becomes equal to 
the E. M. F. of the dynamo supplying the current, and 
this is the speed which would be obtained were the 
motor doing no work and running without friction. 
This condition is impossible in practice, and the 
counter E. M. F. of the motor is always less than the 
E. M. F. of the dynamo. In order to speed up a 



ELECTRICITY FOR ENGINEERS 109 

motor we must arrange it so that it must run faster in 
order to develop an E. M. F. equal to that of the 
dynamo; we can do this by lessening the number of 
turns of wire on the armature, or by lessening the 
magnetism of the fields. In doing so, however, we 
also lessen the capacity of the motor for performing 
work. 

The power that can be obtained from an electric 
motor depends upon two things: the current flowing in 
its armature coils and the strength of magnetism devel- 
oped in the fields. 

Assuming the fields as remaining constant, the power 
of the motor must then vary as the current flowing 
through it. Suppose we have a motor being driven by 
an E. M. F. of no volts and it is doing no work; it 
will be running at full speed and its counter E. M. F. 
will therefore also be very near no volts. If now a 
load be thrown on this motor, it must get more current 
in order to develop the necessary power to carry the 
load. 

Throwing on the load will decrease the speed of this 
motor, and consequently its counter E. M. F. will fall, 
say to 100 volts. The E. M. F. of the dynamo being 
no and the counter E. M. F of the motor lOO, there 
will be considerable current forced through the arma- 
ture of the motor, so that it can now handle the load. 

The current in the armature at all times will equal 

E ~ E' 

— :^ — • where E is the electromotive force of the 

dynamo, E' the counter electromotive force of motor, 
and R the resistance of the motor armature. In order 
that a motor should keep a nearly uniform speed, for 
varying loads, the resistance of its armature should be 
very low, for then a slight drop in counter E. M. F. 



no 



ELECTKICITY FOR ENGINEERS 



will allow considerable current to flow through the 
armature. The above applies particularly to the shunt 
motor shown in Fig. 63. In this diagram C is a double 
pole fuse block, S the main controlling switch, R the 
starting box, or rheostat, M the magnet, which holds 
the arm of the starting box in place when it is brought 




FIGURE 63. 



over against it, F the fields, and A the armature of the 
motor. 

The current enters, say at the right hand fuse, and 
passes to the starting box and along the fine wires 
shown in dotted lines through the fields of the motor 
and coil M to the other fuse. The fields of the motor 
and the little magnet M are now charged, but as yet 



ELECTRICITY FOR ENGINEERS 111 

there is no current passing through the armature and 
no motion. We now slowly move the arm on the start- 
ing box to the right; this admits a little current^ 
limited by the resistance in the starting box, to the 
motor armature and it begins to revolve, and as we 
continue to move the arm to the right, the armature 
gains in speed because we admit more current to it by 
cutting out more and more resistance. When the 
armature attains full speed, the arm comes in contact 
with the little magnet M, and is held there by magnet- 
ism. The whole object of the starting box is to check 
the inrush of current, while the armature is developing 
its counter E. M= F. or back pressure. 

When the armature has attained its normal speed, 
the starting box is no longer in use. If for any reason 
the current ceases to flow, the little magnet M loses its 
magnetism and releases the arm, which (actuated by a 
spring) flies back and opens the circuit so that, should 
the current suddenly come on again, the sudden inrush 
will not damage the armature. 

In Fig. 64 are shown the connections of a series 
wound motor with an automatic release spool on the 
starting box of a sufficiently high resistance so it can be 
connected directly across the circuit. This becomes 
necessary since the field windings are in series with th^ 
armature. 

The speed of a series motor may be decreased by 
connecting a resistance in series with the motor and 
may be increased in speed by cutting out some of the 
field windings. In electric railway work where two 
motors are used on one car, they are usually connected 
in series with each other in starting up and then ?n 
parallel with each other while running at full or nearly 
full speed. The series motor is well adapted to such 



112 



ELECTRICITY FOR ENGINEERS 



work as elex:tric railway work, or for cranes and so 
forth, because it will automatically regulate its speed 
to the load to be moved, exerting a powerful torque 
at a low speed while pulling a heavy load. Such a 
motor, however, requires constant attendance when the 




FIGURE 64. 

load becomes light, as it will tend to ''run away'* 
unless its speed is checked. 

In Fig. 65 we have a diagram of a compound wound 
motor connected with a type of starting box that cuts 
out the armature when current has been cut off the 
lines supplying the motor, as before explained. In 
addition to this there is another electro magnet which 
is traversed by the main current on its path to the 
armature. Should the motor be overloaded by some 



ELECTRICITY FOR ENGINEERS 



lis 



means, the current flowing to the armature v^ouid 
exceed the normal flow. The magnetism thus pro- 
duced would overcome the tension of a spring on the 
armature of the so-called "overload magnet" and cauie 
it to short circuit the magnet which holds the resist- 
ance lever and allow it to fly back and open the arma° 




FIGURE 65. 

ture circuit. By so doing the liability of burning out 
the armature due to overload is reduced to a minimum. 
The compound motor may be made to run at a very 
constant speed, if the current in the series winding of 
the fields is arranged to act in opposition to that of the 
shunt winding. In such a case an increase in the load 
of a motor will weaken the fields and allow more cur- 
vent to flow through the armature without decreasing 



114 



ELECTRICITY FOR ENGINEERS 



the speed of the armature, as would be necessary 
in a shunt motor. Such motors, however, are not 
very often used, since an overload would weaken the 
fields too much and cause trouble. 

If the current in the series field acts in the same 




FIGURE 66. 

direction as that of the shunt fields, the motor will 
slow up some when a heavy load comes on, but will 
take care of the load without much trouble. Fig. 66 
shows a starting box arranged as a speed controller. 
It differs from other starting boxes only in so far that 
the resistance wire is much larger and that the little 



ELECTRICITY FOR ENGINEERS 115 

magnet will hold the arm at any place we desire, so 
that if we leave the arm at any intermediate point the 
motor will run at reduced speed. This sort of speed 
regulation can be used only where the load on the 
motor is quite constant. If the load varies, the speed 
will vary. Another and a better way of varying the 
speed of motors consists in cutting a variable resist- 
ance into the field circuit, as more resistance is cut 
into the circuit the fields become weaker and the 
motor speeds up. If possible, motors should be so 
designed that they can operate at their normal speed, 
and they will then cause little trouble. 

Motors have much the same faults as dynamos, but 
they make themselves manifest in a different way. 
An open field circuit will prevent the motor from start- 
ing and will cause the melting of fuses or burning out 
of an armature. The direction of rotation can be 
altered by reversing the current through either the 
armature or the fields. If the current is reversed 
through both, the motor will continue to run in the 
same direction. A short circuit in the fields, if it cuts 
out only a part of the wiring, will cause the motor to 
run faster and very likely spark badly. If the brushes 
are not set exactly opposite each other, there will also 
be bad sparking. If they are not at the neutral point, 
the motor will spark badly; brushes should always be 
set at the point of least sparking. If it becomes neces- 
sary to open the field circuit, it should be done slowly, 
letting the arc gradually die out; a quick break of a 
circuit in connection with any dynamo or motor is not 
advisable, as it is very likely to break down the insula- 
tion of the machine. 

The ordinary starting box for motors is wound with 
comparatively fine wire and will get very hot if left in 



116 ELECTRICITY FOR ENGINEERS 

circuit long. The movement of the arm from the first 
to the last point should not occupy more than thirty 
seconds, and if the armature does not begin to move at 
the first point the arm should be thrown back and the 
trouble located. 

Alternating Current Motors. By a proper combination 
of two phase or three phase currents it is possible to 
produce a revolving magnetic pole. By placing inside 
of the apparatus which produces this revolving mag- 
netic pole a suitable short circuited armature, this 
armature will be dragged around by the revolving pole 
in much the same way that a short circuited armature 
in a direct current machine would be dragged around 
if the fields were revolved. Such a machine is called 
an induction rnotor. The armature will revolve with- 
out any current entering it from the external circuit. 
This does away with commutators, collector rings, 
brushes, brush-holders, and in fact many of the parts 
which are so necessary in direct current machines. 
The rapidity of the alternations in the external circuit 
determines the speed of the motor. 

Some alternating current motors are known as 
"synchronous" motors. What is meant by synchro- 
nous is, occuring at the same time, or in unison. As 
an example, suppose two clocks are ticking just alike 
so that the pendulums start and stop at the same time; 
we would hear but one tick. These two clocks would 
then be in synchronism. If an alternating current 
generator has 32 field coils and revolves at the rate of 
60 R. P. M., then a synchronous motor with only 4 
field coils would revolve at the rate of 480 R. P. M. 
This motor would operate in synchrony with the gener- 
ator and yet would make 480 R. P. M. while the 
generator made 60 R. P. M. 



CHAPTER VI 

Fuses and Circuit Breakers. Fuses are metal wires or 
strips, generally made of an alloy of lead and antimony, 
the amount of each metal used being so proportioned 
that the wire will melt at a certain temperature. This 
metal is very similar to that used in the fusible plugs 
in boilers. These fuse strips or fuse wires are placed 
in the various circuits in such a manner that the current 
must first flow through the fuse before entering the lights, 
motors or other electrical apparatus. If a short circuit 
should occur, there would be an excessive amount 
of current flow through the fuse and the temperature 
of the metal would be raised to the point where it would 
melt and open the circuit. This would cut off the current 
and save the electrical apparatus from being damaged 
by the excessive current. Fuses are placed in the var- 
ious circuits in accordance with the rules and regulations 
of the National Board of Fire Underwriters. These rules 
require a fuse to be placed in the circuit of every piece 
of electrical apparatus liable to be short circuited, and 
also at points where small wires are tapped onto larger 
ones, unless the main fuse in the larger wire is small 
enough to protect the smallest wire in the circuit. The 
ordinary commercial fuse wire is not intended to melt 
until the current has reached a strength of about twice 
the number of amperes marked on the fuse. A few 
good points to remember in regard to fuses are as fol- 
lows: Unless the fuses are of the new enclosed type 
(fuses entirely encased in small tubes) or unless they 
are under the eye of a constant attendant, they should 
be enclosed in fireproof boxes. This should be done 
to minimize the chance of the red hot metal from a 

117 



118 ELECTRICITY FOR ENGINEERS 

melted fuse dropping into some inflammable material. 
It is a very good plan to enclose all fuses. Fuses 
placed in a hot room will blow at a lower increase in 
current than those in a cool room. Always use copper 
tipped fuses, both for the purpose of getting a good 
contact at the binding screw and for the reason that 
the blowing point of a fuse wire depends on the length 
of the wire. Two pieces of fuse wire of the same 
diameter, but of different lengths, will not blow with the 
same current because the cooling effect of the terminals 
is greater with the shorter fuse. 

In the larger size fuse strips see that the contacts 
between the fuse terminal and the binding post are free 
from dirt and that there is plenty of contact between 
them, otherwise the poor contact will heat up the ter- 
minal and the fuse strip and cause it to blow at a much 
lower current strength than that for which it is marked. 
Oil between the contacts will cause heating and the 
same result. 

From the fact that when a fuse strip has blown the 
current will be off the circuits which are protected b}/ 
the strip until the fuse has been replaced, and this 
takes some time, another device known as the circuit 
breaker has come into general use. The circuit breaker 
is simply a knife switch equipped with a spring which 
tends to open it, and is held in place by a small catch. 
The current passing through the switch also passes 
through the winding of a small solenoid on the inside 
of which is an iron core. When the current passing 
through the solenoid exceeds a certain amount, the 
iron core is drawn up into the solenoid, and in doing 
so strikes the catch holding the switch and releases it, 
thus opening the switch and cutting off the current. 
Circuit breakers are nearly always installed in the cir- 



ELECTRICITY FOR ENGINEERS 



119 




FIGURE 67. 



120 ELECTRICITY FOR ENGINEERS 

cults of generators, although fuses are also used. The 
fuse is rated higher than the circuit breaker, so that 
the circuit breaker will operate first and the fuse only 
operates when the circuit breaker fails to work. Cir- 
cuit breakers are also used to a large extent in protect- 
ing large motors, and the small overload devices used 
on motor starting boxes are simply circuit breakers. 
Fig. 67 shows a view of an I-T-E circuit breaker. S is 
the solenoid and I the moveable iron core. This core 
is adjustable, by means of the washer W, so that it will 
operate at whatever current desired. L is the catch 
which holds the switch. Carbon contact pieces, C C, 
are so arranged that the current is broken on them, 
thus taking the arc off the blades. In Fig. 68 a dia- 
gram of a circuit breaker used for the protection of a 
motor is shown. In this case the circuit breaker is 
double pole; while the one shown in the preceding fig- 
"ure is single pole. 

For small work, such as tap lines and small motors, 
the circuit breaker is too expensive to warrant its use, 
but for capacities of 50 amperes and over it is advisible 
to use the circuit breaker. Circuit breakers are also 
designed and used to prevent the liability of short cir- 
cuits between generators connected in parallel, due to 
the reversal of polarity of one of the dynamos. In other 
words, should one of the dynamos become reversed in 
polarity while working in parallel with other machines, 
the polarity circuit breaker would open the machine- 
switch and cut it out. Circuit breakers of this descrip- 
tion are also used in charging storage batteries. Some- 
times circuit breakers are referred to as overload 
switches. The mechanical operation of these instru- 
ments can be readily understood when examined, as 
they are all of a very simple mechanical construction. 



ELECTRICITY FOR ENGINEERS 



121 



LINE 



J u 



CtRCmT 
BREIAKER 



P.P.S.T, 
SWITCH 




FIGURE 68- 



CHAPTER VII 

ALTERNATING CURRENT DYNAMOS 

Alternating current dynamos are operated upon the 
^ame general principle of magnetic induction as that 
involved in continuous current dynamos. The 
mechanical construction, however, differs considerably 
in the two types of machines. The current produced 
in the two types is identical, but in the direct current 
machine this current is rectified by means of a com- 
mutator; that is, the current constantly flows out one 
wire and back in the other wire, never changing in 
direction in the external circuit. In the alternating 
current dynamo the current is sent to the line exactly 
as it is generated in the armature, flowing out one wire 
and back on the other and then reversing and flowing 
out on the wire on which it has just flowed in, and back 
on the wire on which it had formerly flowed out. An 
illustration which will more fully explain this action 
can be found by supposing the two ends of the cylinder 
of a piston pump were connected by means of a pipe 
and then, having done away with all the valve move- 
ments, the pumps were started. At the beginning of 
the stroke, water would be forced out one side of the 
cylinder around the pipe into the other side of the 
cylinder, and after the piston had reached the end of 
the stroke and started back, the water would then take 
a return course back to where it had started. In this 
case the pump could be likened to the dynamc and 
the pipe to the wires, and the current to the water 
flowing back and forth. The form and windi^ig of 

122 



ELECTRICITY FOR ENGINEERS 



123 



alternating current dynamos varies considerably, but 
they generally follow the plan shown in Fig. 69. In 
the figure the pole pieces are alternately north (N) and 
south (S), while the armature is wound with the same 
number of poles, with the winding so arranged that 
the poles alternate. The fields are excited by direct 
current passing over the field coil windings. This 




.-fo" 



00^ 



9^' 



,(yS 



FIGURE 69. 



direct current is usually obtained from another source 
aside from the current generated in the armature of 
the alternating current dynamo. A separate dynamo, 
called an exciter, is employed for supplying the cur- 
rent to the fields. There are some types of so called 
''composite wound alternating current dynamos'* in 
which a part of the current from the alternator arma- 



1£4 



ELECTRICITY FOR ENGINEERS 



ture is rectified or commutated by means of a commu- 
tator mounted on the same shaft with the armature, 



Armatures are wound 
in two layers. 

-«-« upper coil. 

lower n 




RKbdbIbI 



FIGURE 70. 

and this commutated current passed around the field 
coils in a mannt ^imi^.ar to the dir^^t JUx^rent com- 



ELECTRICITY FOR ENGINEERS 125 

pound wound dynamo. In Fig. 70 we have a diagram 
of connections of a composite wound machine made by 
the General Electric Company. It will be noticed that 
in connection with this dynamo we still employ a sepa- 
rate direct current exciting machine. The object of this 
composite winding is the same as with the compound 
wound direct current dynamo, namely, regulation 
under variable loads without the necessity of changing 
the strength of the field exciting current from the 
exciter dynamo. The winding of the alternate current 
armature consists of the same number of armature coils 
as there are pole pieces in the fields of the machine. 
The outer end of the first armature coil is left free to 
be connected to one of the collector rings, while th'i 
other end of the coil is connected to the inner end of 
the second coil; the outer end of the second coil i? 
connected to the outer end of the third coil, and so on 
through the entire armature. In this class of winding 
you can readily see that while the coils connected from 
the underside or inner ends are under the influence of 
one polarity of field magnetism, the armature coils 
connected from the outer side are under an opposite 
magnetic influence. The purpose of forming the arma- 
ture circuit in this manner may be fully understood 
when it is remembered that the magnetism from the 
north pole of a magnet will induce a flow of electricity 
in a coil of wire in a given direction, while the mag- 
netism of the south pole will induce a flow of current 
in an opposite direction. Now, for the reasons just 
explained, the current in all of the coils of the arma- 
ture will flow in the one direction, but as the armature 
is rotated sufficiently to move the coils from the influ- 
ence of one pole to the influence of the opposite pole 
which is next to it, the action of all the magnetic poles 



126 ELECTRICITY FOR ENGINEERS 

of the field reverse all the inductions in the armature 
coils and cause the current to flow in an opposite 
direction. The number of reversals occurring during 
a revolution is determined by the number of poles that 
the armature coils pass during one revolution. One of 
these armature coils we will assume to be under a 
north magnetic influence and in its rotation it passes 
through a south magnetic influence, thence into a 
north magnetic influence again. The current has now 
alternated or reversed its direction of flow twice and 
has passed through what is called one cycle. If the 
current were making 120 alternations or passing 
through 60 cycles in one second, it would be known as 
making 60 cycles or alternating at the rate 7,200 alter- 
nations per minute. These are the general terms used 
in designating alternating currents. 

By tracing out the circuits in Fig. 70, it will be seen 
that, assuming the current to be flowing into the col- 
lector ring R, it will pass through the upper half of the 
armature winding and out to the commutator C, where 
a part of it will be commutated (or changed into direct 
current), then flowing back around the lower half of 
the armature windings and out to the other collector 
ring R'. On the commutator C the upper line coming 
from the armature is connected to each alternate seg- 
ment, while the lower line is connected to the remain- 
ing segments. The amount of current which is thus 
rectified and flows around the two halves of the -field 
winding, which are connected in parallel, is regulated 
by me^ns of the German silver shunt. The fields are 
also energized by the current generated in the small 
dynamo known as the exciter. 

In Fig. 71 is shown an alternating current dynamo 
with its separate exciter The two collector rings are 



ELECTRICITY FOR ENGINEERS 



127 



shown immediately at the right of the armature, while 
at the right of the collector rings is shown the commu- 
tator from which the current for the composite winding 
of the fields is taken. The current generated by the 
alternator is regulated in the same way as with direct 
current dynamos; that is, by varying the current sent 
around the field windings. This is accomplished by 
the use of a resistance box in series with the exciting 




FIGURE 71. 



current or by means of a resistance box connected in 
the fields of the exciting dynamo. This latter regula- 
tion is of course the more economical, as there would 
be considerable energy wasted were a resistance used 
in the main exciting circuit. Alternating currents are 
generally used where currents are to be transmitted 
long distances, as for instance, where power is derived 
from a water fall situated some distance from the 



128 



ELECTRICITY FOR ENGINEERS 



point of use. Its adaptability for such work is 
apparent, because it can be generated at high voltages 
and transformed down to any voltage desired. It 
requires less copper to transmit it, due to the higher 
voltages employed. By the aid of transformers it can 
either be stepped up to a higher pressure or stepped 
down to as low a pressure or voltage as desired. 
Another great advantage is that, after it has been 
transmitted a considerable number of miles, by the aid 




FIGURE 72. 



of a rotary converter it can be converted into direct 
current. 

Rotary transformers which transform the alternating 
current to a direct current are simply alternating cur- 
rent motors connected to direct current dynamos. 
Sometimes these machines are mounted on the same 
^haft; sometimes they are belted together, and in some 
cases the same windings are used for both machines; a 
2^mmutator being mounted at one side of the armature 



ELECTRICITY FOR ENGINEERS 129 

from which direct current is taken while the alter- 
nating current is taken into the armature on a pair of 
collector rings on the opposite end of the shaft. In 
Fig. 72 is shown a view of a rotary transformer where 
the alternating current is taken in at the right, and 
direct current taken off at the commutator on the left. 
By single phase we understand that the current flows 
out, gradually increasing in strength, then dying away 
and reversing in direction and again increasing and 
dying away. This action is shown by the curve in 




FIGURE 73. 

Fig. 73. Although the single phase alternating cur- 
rent system is in advance of the direct current system 
for electrical power transmission, because permitting 
electrical power to be transmitted long distances at 
high potential, which can be readily increased or 
reduced by means of transformers, the single phase 
system is limited by the difficulty in obtaining a satis- 
factory self starting motor; therefore the use of the 
single phase current has been confined almost entirely 
to transmitting current for lighting. The development 
of the polyphase (two phase and ihree phase) alter- 



130 



ELECTRICITY FOR ENGINEERS 



nating systems possess all the advantages of the single 
phase system and at the same time permits the use of 
motors having not only most of the valuable features 
of the continuous current motors, but also some advan- 





FIGURE 74. 



tages over them. In the two phase system two cur- 
rents displaced 90 degrees from each other and 
otherwise exactly similar to the single phase currents 
are used. In the three phase system three currents 
separated 120 degrees are used. These currents are 
shown in Fig. 74. 




FIGURE 75. 



In Fig. 75 is shown the principle upon which the 
transformer used in alternating current work are opera- 
ted. Two separate coils of wire are wound on a ring 



ELECTRICITY FOR ENGINEERS 



131 



of laminated iron. One of the coils contains a num* 
ber of turns of fine wire, while the other contains only 
a few turns of large wire. When an alternating cur- 
rent is sent around the coils of fine wire, generally 
called the primary, a current will be induced in the 
coil of heavy wire, or secondary. The amount of cur- 
rent induced in the larger wire will be relatively 
greater in amperes and less in potential than that of 
the fine wire circuit. This ratio is almost entirely 
dependent upon the relative number of turns existing 




FIGURE 76. 



between the large and the small wires. To illustrate, 
suppose we had a current of lo amperes at a pressure 
of 1,000 volts in the primary, and there were ten times 
as many turns of wire in the primary coil as in the 
secondary, then we would get a current of lOO amperes 
at a pressure of lOO volts in the secondary coil. This 
same relation would hold true whatever the ratio 
between the number of turns 'on the two coils might 
be. In Fig. 76 is shown a core of iron having on one 
end a primary coil connected to a battery. On the 
other end of the core is another coil connected to the 



132 ELECTRICITY FOR ENGINEERS 

ends of which is an incandescent lamp. By making 
and breaking the battery circuit the lamp may be made 
to flash up, due to the great voltage induced in the 
secondary coil. This is a good thing to remember 
when working with a dynamo or motor. Do not 
quickly break the shunt field connection, as the 
increased voltage due to the current induced by the 
field magnet when the circuit is broken is liable to 
puncture the insulation and necessitate the re-winding 
of the field coil. 



CHAPTER VIII 



METERS 



Volt and Ampere Meters. Two of the most important 
instruments used in electrical work are the voltmeter 
and amperemeter, the latter generally called ammeter. 
Classed with these instruments is a meter of an im- 
portant nature called the wattmeter. We will first 
become acquainted with the voltmeter, which is an 
instrument, as its name implies, for measuring the 
voltage or potential or electromotive force between two 
wires. The general construction of this instrument is 
shown in Fig. "JJ, 

In this diagram we show an instrument on the order 
of the Weston meter. This will serve as a good illus- 
tration that the operation of meters is very similar to 
the operation of motors. A permanent magnet, M, 
causes a magnetic flux across the air gap G, and 
situated in this gap is a bobbin, B, on which is wound a 
number of convolutions or turns of copper wire. The 
bobbin is made to revolve on jeweled bearings. The 
object of the jewel bearing is to have the instrument as 
much devoid of mechanical friction as possible. Two 
springs, S, one above and one below the bobbin, carry 
the current to the movable part of the meter. If the 
current is now caused to flow around the coil of wire, 
it will produce a torque or twist which will move the 
bobbin again the two hair springs, S. Like magnetic 
poles repel each other and unlike magnetic poles 
attract each other. The current flowing around the 

133 



134 



ELECTRICITY FOR ENGINEERS 



movable bobbin produces magnetism, and the quantity 
or strength of magnetism so produced is proportional 
to the amount of current which the pressure or voltage 




FIGURE 77 



will force through the winding of the movable bobbin 
so that the bobbin will continue to move until the 
torque exerted by the current equals the counter torque 
exerted by the spiral springs. A pointer, fastened to 



ELECTRICITY FOR ENGINEERS 135 

the shaft upon which the bobbin is mounted, passes 
over a graduated scale and indicates the pressure or 
volts. The capacity of this meter in volts will vary as 
the resistance of the wire connected in series with the 
bobbin varies. We will assume that we have a meter 
whose pointer reads from o to 125 volts. If we desired 
this same meter to read from o to 250 volts, we would 
put a resistance in the meter which would be twice as 
great as the one contained in the meter when reading 
from o to 125 volts. The permanent magnet of this 
meter is made of Tungsten steel, and this steel is arti- 
ficially aged so that when the instrument leaves the 
factory the magnetizing power of the magnet will 
remain constant for a number of years. The current 
is brought into the instrument through the binding 
posts A and C, but before passing through the wire on 
the bobbin the current must pass over a path of very 
high resistance, R. This resistance is proportioned to 
the amount of pressure the meter is made to indicate, 
and in commercial construction instead of making 
bobbins of variable resistances, the bobbins are all 
made alike, and this dead resistance, R, is varied to 
comply with the pressure that it is to indicate with the 
instrument. In voltmeters used on a 500 to 600 volt 
circuit, this resistance will measure from 65,000 to 
75,000 ohms. The current which flows through the 
winding on the bobbin at full voltage is very small, and 
when registering no volts amounts to about one seven- 
hundredth of an ampere. Since it is the number of 
ampere turns that produces the magnetic density in an 
electro magnet, it can be seen that even one seven- 
hundredth of an ampere, if passed around a bobbin a 
considerable number of times, will produce quite a 
strong magnetic flux and gull. Voltmeters are often 



136 ELECTRICITY FOR ENGINEERS 

referred to as being "dead beat." What is meant by 
dead beat is the tendency of the pointer to move from 
one position to another with very little or no swinging 
to and fro. In this type of voltmeter this dead beat 
effect is produced in the following manner: The core 
of the bobbin B being constructed of copper, when a 
current flows over the winding of the bobbin and causes 
it to revolve, eddy currents are produced in the copper 
(in much the same way that current is produced in the 
revolving armature of a dynamo), and these eddy cur- 
rents tend to arrest the motion of the bobbin. In the 
best voltmeter construction the resistance wire used is 
made of a metal which will not vary much in resistance 
at different temperatures. It can readily be seen that, 
were a meter which was constructed and correctly 
calibrated at 70° F., surrounding temperature, mounted 
on switchboard in an engine-room with the temperature 
at 90° or 95°, the meter would not register absolutely 
correct, because the resistance of the wire would be 
considerably increased, due to the increase of the sur- 
rounding temperature. The effect of this would be a 
smaller flow of current at an equal voltage through 
the bobbin in the meter, and consequently a smaller 
amount of magnetism and a lower reading of the in- 
strument. 

We will assume that a copper cable of about the size 
of one's wrist is conducting a current of about 
three thousand amperes. Now, if a monkey wrench or 
hammer were to be lying within a few inches of this 
cable, before current was flowing, the monkey wrench 
or hammer would be attracted to the cable. The 
rapidity with which the monkey wrench would be 
attracted to the cable would be proportional to the 
weight of the iron in the wrench and the amount of the 



il 



ELECTRICITY FOR ENGINEERS 137 

current flowing through the cable. This, I think, will 
explain an electrical phenomenon which will assist us 
to understand what are called the magnetic vane volt- 
meters and ammeters. This principle is shown in 
Fig. 78. 

A certain amount of current passing over the path 
A, which consists of several turns of wire, will attract 
an iron form, B, mounted on the spindle with the 




FIGURE 78. 

pointer. The attraction will be proportional to the 
amount of current flowing over the copper conductor. 
The advantage of such an instrument is its simplicity, 
but the disadvantage is its inaccuracy. Its simplicity is 
apparent, and its inaccuracy is due to the residual 
magnetism that remains in the iron part B when the 
current through the conductor has been reduced. 
When the indicator is caused to move upward on the 
scale, the instrument will register practically correct, 



138 ELECTRICITY FOR ENGINEERS 

but as the flow of current over the conductor A dimin- 
ishes or decreases, the residual magnetism remaining 
in the iron part B will have a tendency to cause it to 
lag back. Amperemeters are constructed on practi- 
cally the same lines as explained in the construction of 
voltmeters, except that in ammeters the whole current 
to be measured passes through the coil A, this coil 
being made of comparatively few turns of large wire, 
while in voltmeters the resistance is very high. 
Ammeters are placed in series with one of the leads 
and voltmeters in shunt with the current to be meas- 
ured. In some ammeters a resistance block, usually 
called a shunt, is employed, over which the main cur- 
rent is caused to flow, and the ammeter is connected to 
both ends of this resistance block. In this way only a 
very small portion of the total current is caused to 
flow through the ammeter. In this case a milli-volt- 
meter, with the scale graduated to amperes, is 
employed. By Ohm's law we know that the voltage is 
equal to the current times the resistance, E = CR. 
The resistance remaining constant, the voltage is pro- 
portional to the current, so that the amount of current 
sent through the milli-voltmeter or ammeter is exactly 
proportional to the current flowing through the shunt. 
Fig. 79 shows connections for ammeters which carry 
the entire current and those used with a shunt. 

The object of such a construction is apparent. In 
the installation of the switchboard, where each 
ammeter registers several thousand amperes, it is not 
necessary to construct the large conductors in such a 
manner that the total current is caused to flow through 
the ammeter. For each i,ooo amperes passing over 
the shunt only about one-half an ampere will pass 
through the ammeter, and the little bobbin will then 



ELECTRICITY FOR ENGINEERS 



139 



cause a deflection of the pointer in the meter and the 
pointer will register 1,000 amperes. Meters of this 
description are usually connected to their resistance 
blocks by a pair of No. 16 flexible lamp cords. When 
installing meters of this class, never cut off any of the 



/-\ 






Shij^*^ 



o 
Z 
< 



FIGURE 79. 

flexible cord which is supplied with the ammeter, as 
the resistance of the cord becomes a part of the resist- 
ance in the meter. By cutting off some of this cord 
it can be readily seen that the meter will register more 
current than it should. 



140 



ELECTRICITY FOR ENGINEERS 



Another kind of meter is constructed on the 
solenoid principle, and is shown in Fig. 8o. In this 
instrument the helix is a bare copper wire and is wound 
in an open coil form. It is curved in the shape of a 
segment of a circle, the center of which is at the pivot 
on which the needle is suspended. The pointer or 
needle is attached and projects downward to the scale. 
The helix is made of copper rod or is cast to the shape 




FIGURE 80. 



required. Being of an open coil type, it is not neces- 
sary that it be insulated with insulating material 
because the air spaces between the turns becomes the 
insulation. Although not the best insulator by any 
means, there are few substances which possess better 
insulating qualities than air, although on account of its 
absorption of moisture, it becomes often a much poorer 
insulator than many other materials. In this type of 



ELECTRICITY FOR ENGINEERS 



141 



instrument it will be seen that as the number of 
amperes flowing over the coil is increased it produces 
an increased electromagnetic pull on the iron section 
or core entering it. As this electro magnetic pull is 




FIGURE 81. 



increased, the core moves up into the helix and causes 
a deflection of the pointer across the scale on the 
instrument. This type of instrument has the same 
objection as that of the magnetic vane instrument, 



142 ELECTRICITY FOR ENGINEERS 

namely, residual magnetism of the iron, and hence 
error in the reading while the current flowing is being 
diminished. 

Another style of simple ammeter or voltmeter is 
shown in Fig. 8i. This instrument consists of a frame 
made of non-magnetic material, around which the wire 
is wound, the ends of the wires being connected to the 
binding posts. The armature of this instrument, as in 
all other similar instruments, is connected to the 
pointer, and may be constructed of several pieces of 
iron. The principle of its working is similar to that 
described above, in that the armature tends to set 
itself at right angles to the wire through which the 
current passes. This style of instrument is used where 
current is liable to flow in either direction. 

A simple form of meter for measuring current is 
shown in Fig. 82. Here we have an amperemeter 
which consists of a strip of copper fastened to a block 
of wood or other insulating material, as shown at A. 
A piece of magnetized steel, B, to which a needle, C, is 
attached, swings on a pivot or shaft which is suspended 
at the bridge D. A scale is provided from which the 
number of amperes flowing can be obtained. The 
needle is rigidly attached to the magnetized steel B and 
moves with it. The action of this instrument is as fol- 
lows; When a magnetized piece of steel is brought near 
to a conductor through which a current of electricity 
is passing, the magnetized steel tends to set itself at 
right angles to the direction of the current. The 
stronger the current becomes, or the more highly mag- 
netized the piece of steel may be, the nearer to a posi- 
tion of right angles the armature will assume. It is 
not practical to use this construction of an instrument 
to cover a range of more than one-half of a risrht 



ELECTRICITY FOR ENGINEERS 



148 



angle, for when the needle moves through an angle of 
about 50 degrees, it will require a much greater 
increase of current in proportion to the movement to 
obtain the deflection and the additional degree of the 
indicating needle. Such an instrument as the above 
may also be used to determine the direction of flow of 




(Elf^mf-k) 




FIGURE 82. 



current in a wire and is sometimes quite convenient on 
arc circuits which are liable to have their currents 
reversed either by wrong plugging of the board or the 
reversing of polarity in the dynamo. 

Voltmeters and ammeters used with alternating cur- 
rents must, of course, differ in some respects from 



ii4 ELECTRICITY FOR ENGINEERS 

those employed for continuous currents. Alternation 
of the current does not permit the utilizing of the mag- 
netic effect of the current to the same extent or in 
exactly the same manner as continuous currents, but 
when the cores of magnets are built up of soft iron 
wires of small diameter, the resulting attraction 
between coil and core is similar, though not so strong 
as between a coil carrying direct current on a solid 
iron core. 

Another type of ammeter and voltmeter used with 
alternating or direct current is known as the hot wir- 
instrument. A rather long, thin platinum wire is 
placed in the circuit and so arranged that its elonga 
tion or expansion resulting from the heating effect ot 
the current passing over it is made to operate a pointer 
mounted on a jeweled bearing. These instruments 
absorb but little current and are claimed to be per- 
manently correct. This class of instrument may be 
used on either direct or alternating current, and when 
used on alternating current the frequency or alterna- 
tions make no difference in the operation of the instru- 
ment. It is also unaffected by external magnetic fields, 
such as a neighboring dynamo or motor, and can be 
used close to a wire conducting current without being 
affected in its accuracy. When used as an ammeter it 
is connected in shunt with a resistance placed in the 
main circuit in the same manner as described for direct 
current ammeters, and in this way but a very small 
proportion of current is made to pass over the instru- 
ment. Separate resistances are also furnished with th 
instruments; so that by connecting these in series witi 
the instrument they can be used over a very wide range. 

Wattmeters. A few years ago, where current was 
«o'ld by central stations to consumers, oi in any other 



ELECTRICITY FOR ENGINEERS 145 

place where it was desirable to measure the power fur 
nished in the form of electricity, there were several 
kinds of differently constructed meters used to measure 
the amount of current. Some of these meters were 
based on the chemical action of the current; the current 
in passing to the work depositing metal from one plate 
to another. The plates or terminals of the meters 
were weighed before being placed in the circuit and 
again weighed on being taken out, the amount of metal 
having been deposited determining the amount of cur- 
rent used, as explained in the fore part of the book. 
Of late, however, most of the recording wattmeters in 
use are operated on the principle of the Thomson 
wattmeter. As has been explained under the definition 
of units, the work done (watts) is equal to the current 
(amperes) multiplied by the electromotive force (volts), 
or W = C X E. For a wattmeter to register correctly it 
must take a record of the volts and amperes. 

The Thomson wattmeter is simply a small motor in 
which the armature is used as a voltmeter and the 
fields as an ammeter. The armature is wound with fine 
wire and is connected to a small commutator made up 
of metal bars. Two very thin metal brushes bear on 
this commutator and carry the current to and from the 
armature. The armature is connected across the mains 
in just the same way as a voltmeter would be connected. 
The fields are wound with a coarse wire and are con- 
nected in series w^ith the main circuit, thus acting as an 
ammeter.. It can readily be seen that with the arma* 
ture influenced only by the voltage, and the fields by 
the current passing through the mains, the two acting 
together will correctly measure the power supplied. 
As the voltage rises or lowers, the speed of the arma- 
ture will be affected accordingly, and as the current 



146 



ELECTRICITY FOR ENGINEERS 



through the fields varies the electromagnetic effect 
produced by the fields and in which the armature 
revolves will vary, thus also varying the speed. Bv 
reference to Fig. 83, the fields F F are connected in 
series with one of the mains and the armature A is 




o IMMMA 



^ 

^ 



+ g ll 



<n 



.r: 



Til 



FIGURE 83. 



connected across the mains. Fig. 84 is a simplified 
diagram. Attached to the shaft on which the arma- 
ture rotates is a copper disc which revolves between 
the poles of a permanently magnetized steel magnet. 
Eddy currents are generated in this copper disc as the 



ELECTRICITY FOR ENGINEERS 147 

armature rotates, thereby acting as a brake against 
which the armature must work. Connected to the top 
of the shaft is a train work of wheels which move small 
pointers over the dials on the face of the instrument 
and record the amount of current which has passed 
through the meter. As no iron is used in either the 
armature or fields of the motor, the meter can be used 
on either alternating or direct current. 

In Fig. 85 we show a two wire meter with the case 
removed. 

In Fix. 86 a three wire meter is shown. 

Directions for Reading Meter Dials. To correctly read 
the sum indicated on the dial of a recording meter, the 



AAAAA7==WVW 




FIGURE 84. 

directions given herewith should be thoroughly under- 
stood and carefully followed. 

The figures (i,ooo, 10,000, etc.) under or over each 
dial refer to a complete revolution of the hand at that 
dial. 

Therefore, each division on the dial to the extreme 
light indicates not one, two, three, or four thousands 
of units, but one, two, three, or four hundreds of units. 

A complete revolution of the hand counts one thou- 
sand, and will have moved the hand on the second dial 
one division. Thus in reading Diagram No. 6, Fig. 
87 the first dial (that on the extreme right) indicates 
700, not 7,000. 



148 



ELECTRICITY FOR ENGINEERS 



A hand to be read as having completed a division, 
must be confirmed by the dial before it (to the right). 
It has not completed the division on which it may 
appear to rest, unless the hand before it has reached 




rROM GENERATOR 



FIGL'KE So. 



or passed o, or, in other words completed a revolution. 
For this reason it will be found easier and quicker to 
read a dial from right to left, as shown by reading Dia- 
gram No. 2, Fig. 87. 



ELECTRICITY FOR ENGINEERS 



149 



The first dial (the extreme ri^jht) indicates 900. The 
second hand apparently rests on 0, but since the first 
rests only on 9 and has not completed its revolution, 




FIGURE 86. 



the second dial also indicates 9. This 9, placed before 
the 900 already obtained, giv^es 9,900. 

This is also true of dial 3. The second hand, at 9, 
has not quite completed its revolution, so the third has 
not completed its division, therefore another 9 is 



150 ELECTRICITY FOR ENGINEERS 

obtained, making 99,900. The same is true of dial 4, 
making 999,900. 

The last dial (the extreme left) appears to rest on i, 
but since the fourth is only 9, the last has not com- 
pleted its division, and therefore reads 0. The total 
reading is 999,900. 

The hands are sometimes slightly misplaced. In 
Diagram No. 8 the first diagram (the extreme right) 
reads 0, which gives 000. The hand of the second 
dial is misplaced. As the first registers 0, the second 
should rest exactly on a division; therefore it should 
have reached 8, making 8,000. The third hand is 
apparently on 3, but since the second hand is at 8, the 
third cannot have completed a division and must, 
therefore, indicate 2. The two remaining dials are 
correct, and make a total of 9,928,000. 

In Diagram No. 9, the second dial hand is mis- 
placed, for since the first indicates i, the second should 
have just passed a division. As it is nearest to 8 it 
must have just passed that figure. The remaining 
three dials are approximately correct. The total indi- 
cation is 9,918,100. 

In Diagram No. 10, the second and fourth dial 
hands are slightly behind their correct position, but 
not enough to mislead in reading. The total indica- 
tion is 9,928,300. 

By carefully following these directions little diflfi- 
culty will be found in reading the dial, even when the 
hands become misplaced. 

Note whether there is a constant marked on the 
dial. If there is, multiply the dial reading by the 
constant With constant 3^, multiply by >^; that is, 
divide by 2. 

The "constant" of a meter is the term applied when 



ELECTRICITY FOR ENGINEERS 



151 



No.1=^1.111.100 



f^ 1000000 100000 10000 (~\ 

WATT METER X^^lj/ 

loooooooQENERAL ELECTRIC CO. '''"' ^ 

^Watt HfS. Constant Watt Hfs.CJ , 
No.2= 999.900 

'O ■ 



No.6 = 99.700 




WATT METER 

loooooooQENERAL ELECTRIC CO. ^o<"> ^ 
CJwatt Hrs Constan t Wan Hfs.vJ ^ 

No.3 = 1.000.100 




10000000QENERAL ELECTRIC CO. '°°« ^-. 

^Watt Hrs. Constant Wan HrsNsJ 
No. 4. =9.999.400 



O 



1000000 '100000 




WATT METER 

.oooooooQENERAL ELECTRIC CO. ^o"" ^ 

WWatt Hrs. Constani Watt Hts.vJ ^ 
No. 5 =909.100 



1000000 100000 



o 



\!JLX WATT METER X,±V 

loooooooeENERAL ELECTRIC CO. ^»°o ^ 

VJ Walt Hrs. Constant .Watt Hrs.vJ 





10000000QENERAL ELECTRIC CO ^o«» ^ 

O Watt Hrs. Constant Wat^ HrsLJ 



No.7=9.912.100 



r~\ 1000000 100000 10000 (~^ 



m 



Vj>/ WATTMETER 

10000000QENERAL ELECTRIC CO. '^^'^ ^ 

O Watt Hrs. Constar\t Watt H-rs.O 



No. 8 =9.928.000 



r~^ lOOOOOO 100000 





WATT METER 

loooooooQENERALELECTRIC CO '»«» ^ 

vJ Watt Hrs. Constant Watt Hrs. L^ 
No. 9 = 9.918.100 ■ 




looooowQEfiERAL ELECTRIC CO. "«• ^ 

QjWatt Hrs. Constarit Watt Hrs.W 



(O 



No.10 = 9.928.300 




l±y WATT METER 

loooooooQENERAL ELECTRIC CO. '<««> ^ 

\Jwatt Hrs. Constar^t Watt HnKJ. 



iflGURE 87. 



152 ELECTRICITY FOR ENGINEERS 

the meter is constructed to run at a lower speed than 
what would be necessary to measure the true number 
of watts which has passed through it. P'or instance, 
if the constant is 2 and the meter has registered 5,000 
watt-hours, then the meter having run only half as fast 
as it should, we multiply 5,000 by 2, which gives us 
10,000 watts as the actual amount that has passed 
through the meter. This scheme becomes necessary in 
order to register a large amount of current with a 
meter smjall in bulk or size. For convenience the 
maker often takes a 220 voltmeter which would read 
the number of watts direct on the dial at 220 volts and 
sells it for a no voltmeter by marking a constant on 
the dial of the meter. 



CHAPTER IX 

Arc Lamps. The principle on which the arc lamp oper- 
ates is shown in Fig. 89. Current is caused to flow 
from one carbon point to another through a space or gap 
between the carbons. The heat of the arc is suificiently 
high to disintegrate the carbon and reduce it to a vapor, 
this vapor filling the space between the carbon points. 
The current passes over this space in a bow-shape path 
or arc, and it is from this fact that the lamp gets its 
name. The arc is constantly moving, and generally 
revolves around the carbon points. This can be easily 
seen by looking closely at a burning lamp through a 
smoked glass. After a lamp has been burning for 
some time on direct current the carbons assume the 
shape shown in Fig. 88, the upper or positive carbon 
assuming a cup shape, while the lower carbon gener- 
ally burns to a point. This cup shape formation on 
the upper or positive carbon acts as a reflector to 
throw the light downward. The positive carbon burns 
away about twice as fast as the negative carbon and 
lamps must be trimmed accordingly. Sometimes the 
current feeding arc lamps (on direct current systems) 
becomes reversed, either through the dynamo reversing 
its polarity or through wrong plugging of the switch- 
board. The lamps will now burn "upside down,'* or, 
in other words, the bottom carbon will be the positive 
one. In such a case, if let go, the carbon holders 01 
the lamp will be burned and the lamp will burn for 
only half the time for which it was intended, owing to 
the fact that the lower or negative carbon is only one* 
half a§ long as the upper or positive carbon. Such '^ 

153 



154 ELKCTRICITY FOR ENGINEERS 

condition can be determined by either of the following 
#ays: See if the light is being thrown downwards. 
See which carbon is burning away the faster. Raise 
the carbons and notice the formation of the carbon 
tins. When the carbons are separated it will be 
noticed that the tip of one carbon is considerably hot- 
ter than the other and is heated a longer distance from 
the point; this is the positive carbon. 




FIGURE 



The action of the arc lamp used on direct current 
constant current systems is shown in Fig. 89. Current 
passes through wire T and over the coarsely wound 
solenoid M, thence down to the carbon, across the 
arc or crater, into the negative carbon and out again 
on the wire T'. The regulating action is as follows: 
A coil M', constructed of fine wire and of high resist- 
ance, is connected in shunt across the arc. The action 
of the current flowing through the solenoid M across 



ELECJTRICITY FOR ENGINEERS 



155 



QT 



"^ta 



ihe crater or arc produces a magnetic pull on the 
solenoid core A and causes a separation of the car- 
bons. As these carbons burn away the resistance 
across the crater increases and a very small portion of 
the main current is caused to flow through the shunt 
coil M'. The magnetic pull of the shunt solenoid 
overcomes that of the series solenoid with the result 
that the solenoid core A is drawn into coil M' and the up- 
per carbon thus lowered, de- 
creasing the gap at the arc. In 
this way a constant regulation 
is going on, tending to keep 
the two carbons at a uniform 
distance apart. The upper car- 
bon rod is held by means of a 
clutch. When the carbons have 
burned away, so that the lower- 
ing of the solenoid does not 
lower them to the proper ex- 
tent, the clutch is released and 
the carbon drops, thus feeding 
the lamp. Some lamps are 
manufactured wherein the lower 

carbon is positive. This causes the light emitted from 
the crater to be projected upwards. The arc lamp 
frame is supplied with a shade on which the light cast 
from the arc is reflected downward. The advantage of 
this system is to obtain a better diffusion and distribu- 
tion of the light beneath the arc lamp. This lamp 
is not now generally used. 

Fig. 90 shows a diagram of connections for the 
improved Brush arc lamp. These lamps are used on 
constant current or series systems and their action 15 
as follows: 




FIGURE 89. 



156 



ELECTRICITY FOR ENGINEERS 



The carbons should rest in contact when the lamp is 
:.ut out. When the switch is opened, part of the cur* 



-zC\ 




FIGURE 90. 



rent from the positive terminal hook P goes through 
the adjuster to the yoke and thence through the carbon 



ELECTRICITY FOR ENGINEERS 157 

rod and carbons to the negative terminal hook N. 
The rema/nder of the current goes to the cutout 
block, but, as the cutout block is closed at first, the 
current crosses over through the cutout bar to the 
starting resistance, and so to the negative side of 
the lamp. A part of it, however, is shunted at the 
cutout block through the coarse vi^ire of the magnets 
and so to the upper carbon rod and carbons and out. 
This shunted current energizes the magnet and so 
raises the armature which opens the cutout and at the 
same time establishes the arc by separating the car- 
bons. 

The fine wire winding is connected in the opposite 
direction from the coarse wire winding, and its attrac- 
tion is therefore opposite. When the arc increases in 
length, its resistance increases, and consequently the 
current in the fine wire is increased. The attraction of 
the coarse wire winding is therefore partly overcome 
and the armature begins to fall. As it falls, the arc is 
shortened and the current in the fine wire decreases. 
The mechanism feeds the carbons and regulates the 
arc so gradually that a perfect, steady arc is main- 
tained. 

The fine wire of the magnets is connected in series 
with the winding of a small auxiliary cutout magnet 
at the top of the mechanism. 

' This magnet, which also has a supplementary coarse 
winding, does not raise its armature unless the voltage 
at the arc increases to 70 volts. The two windings 
connect at the inside terminal on the lower side of 
auxiliary cutout magnet, and the current from the fine 
wire of the main magnets passes through both wind- 
ings and then to the cutout block and so to the starting 
resistance and out. 



158 ELECTRICITY FOR ENGINEERS 

If the main current through the carbon is interrupted 
(as by breaking of the carbons) the whole current of 
the lamp passes through the fine wire circuit. Before 
this excessive current has time to overheat the fine 
wire circuit, it energizes the auxiliary cutout mag- 
net, and closes a circuit directly across the lamp 
through the coarse wire on the auxiliary cutout to 
the main cutout block, and thence to the negative 
terminal. 

The auxiliary cutout operates instantly, and prevents 
any danger to the magnets during the short period 
required for the main armature to drop and throw in 
the main cutout. When the main cutout operates, the 
armature of the auxiliary cutout falls, because there is 
not sufficient current in that circuit to energize the 
magnet. 

The voltage at which the auxiliary cutout magnet 
operates depends on the position of its armature, 
which is regulated by the screw securing the armature 
in position. It should not be adjusted to operate at 
less than 70 volts. 

One of the three methods of suspension may be used 
for Brush lamps. If chimney suspension, which is the 
most common, is adopted, the wire, cable or rope used 
to suspend the lamp must be carefully insulated from 
the chimney. For this purpose a porcelain insulator 
should be inserted between the support and the lamp, 
as shown in Fig. 91, 

Hook suspension may be used to advantage in some 
places, but great care must be taken to insulate the 
supporting wires from any conductors, as the hooks 
form the terminals of the lamps. 

The most convenient arrangement for indoor use is 
to suspend the lamp from a hanger board. The porce- 



ELECTRICITY FOR ENGINEERS 



159 



iain base of the hanger board prevents short circuits 
or grounds. 

A protecting hood is not necessary for outdoor use, 
as the lamp chimney and its base are one casting and 
effectually exclude rain or 
snow water. 

The lamps run on circuits 
of 6.6 amperes for 1,200 and 
9.6 amperes for 2,000 nom- 
inal candlepower. In case 
it is necessary to run a lamp 
on a circuit differing from 
the standard, the lamp may 
be adjusted by moving the 
contact on the adjuster. 
About one ampere either 
above or below the normal 
may be compensated for by 
this means. 

Permanent adjustment for 
special circuits of variation 
greater than one ampere is 
made by filing the soft iron 
armature. The clutch should 
be so adjusted that the cen- 
ter of the armature is ||- in. 
above the plate when the trip 
on the first rod is touching 
the bushing, and ||- in. when 

the trip on the second rod is in a similar position. 
A small gauge is convenient for adjusting the clutch. 
The position of the trip of the clutch determines the 
feeding point of the lamp. 

After thoroughly repairing and cleaning the lamp, it 



1 




h 




■rf 








':n 








1 

/ 1 

■■ 1 
1 




'/ ■ 




: . :;.:.,:i 


^M 


1 


k 




Ji 


"rj 


1 ' 


teft«?»irt*:*ss**5;Ss 






l..~-^ rv.;,w4 



FIGURE 91. 



ICO ELECTRICITY FOR ENGINEERS 

should be run a short time before installing. Lamps 
should not be tested in an exposed place, as a strong 
draft of air will cause unpleasant hissing which may be 
mistaken for some internal trouble. 

Lamps should not hiss or flame if good carbons are 
used. A voltmeter should always be used when adjust- 
ing or testing. 

The lamp terminals are marked P (positive) and N 
^regative) and should be connected into circuit accord- 
ingly. 

The carbons should be solid and of uniform quality. 
For the best results, the upper carbon should be 
12 in. X j\ in., and the lower 7 in. x -^^ in. The stub 
of the upper carbon may then be used in the lower 
holder when retrimming. 

At each trimming the rod should be carefully wiped 
with clean cotton waste. If any sticky or dirty spots 
* ppear, which cannot be readily removed with waste, 
^se a piece of well-worn crocus cloth, always being 
careful to use a piece of clean waste before pushing 
the rod into the lamp. It should never be pushed up 
*rto the lamp in a dirty condition. 

The carbon rod may be unscrewed and removed by a 
small screw driver or small strip of metal inserted in 
the slot cut in the rod cap. The cap will remain in 
the hole through the yoke when the rod is taken 
■^ut. 

In Fig. 92 an interior view of the Thomson-Houston 
arc lamp is shown. This lamp is also used on con- 
stant current systems. 

The lamps should be hung from the hanger boards 
provided with each lamp, or from suitable supports of 
wire or chain. 

As the hooks on the lamp form also its terminals, 



ELECTRICITY FOR ENGINEERS 



161 



they should be insulated, where a hanger board is not 
used, from the chains or wires used to support the 
lamp. 




FIGURE 92. 



When the lamps are hung where they are exposed to 
the weather, they should b-,. covered with a metal 
hood, to prevent injury from rain and snow. 



10^ ELECTRICITY FOR ENGINEERS 

In such cases, care should be taken that the circuit 
wires do not forma contact on the metal hood and 
short circuit the lamp. 

Before the lamps are hung up they should be care- 
fully examined to see that the joints are free to move, 
and that all connections are perfect. 

No lamp should be allowed to remain in circuit, 
with the covers removed and the mechanism exposed. 
Such practice is dangerous, and in violation of insur- 
ance rules. 

The object of testing the lamps in the station is to 
find any defects, if such exist, and to test all the con- 
ditions of running before delivering them to custom- 
ers. The lamps should not be hung up in their 
respective places in the external circuit, until every- 
thing is running with perfect satisfaction. 

The tension of the clamp which holds the rod is 
adjusted by raising or lowering the arm at the top of 
the guide rod. (See Fig. 93.) If the tension is too 
great the rod and clutch will wear badly and the feed- 
ing will be uneven, causing unsteadiness in the lights. 
Too little tension will not'allow the clutch to hold up 
the rod and any sudden jar to the lamp will cause the 
rod to fall and the light to go out. 

The double carbon, or M lamp, should have the ten- 
sion of the second carbon a trifle lighter than the first 
one. 

When adjusting the tension, be sure to keep the 
guide rod perpendicular and in perfect line with the 
carbon rod; it should be free to move up and dov/n 
without sticking. 

The tension of the clutch in the D lamp should be 
the same as that of the K lamp. It is adjusted by 
tightening or loosening the small coil spring from 



ELECTRICITY FOR ENGINEERS 



163 



the arm of the clutch to the bottom of the clamp 
stop. 

To adjust the feeding point in the K lamp, press 
down the main armature as far as it will go, then push 




FIGURE 93. 



up the rod about one-half its length, let go the arma- 
ture and then press it down slowly and note the dis- 
tance of the bottom side of the armature above the 
base of the curved part of the pole. When the rod 



164 ELECTRICITY FOR ENGINEERS 

just feeds, this distance should be % in. If it is not, 
raise or lower the small stop which slides on the guide 
rod passing through the arm of the clutch, until the 
carbon rod will feed when the armature is % in. from 
the rocker frame at base of pole. 

To adjust the feeding point of the M lamp, adjust 
the first rod as in the K lamp. Then let the first rod 
down until the cap at the top rests on the transfer 
lever. The second rod should feed with the armature 
at a point yV ^^- higher than it was while feeding the 
first rod, that is, it should be y\ in. from rocker frame 
at base of pole. 

The feeding point of the D lamp is adjusted by slid- 
ing the clamp stop up oi down, so that the rod will 
feed when the relative distances of the armature of the 
lifting magnet and the armature of the shunt magnet 
from rocker arm frame are in the ratio of i to 2. 
There should be a slight lateral play in the rocker, 
between the lugs of the rocker frame. 

The armatures of all the magnets should be central 
with cores, and come down squarely and evenly. 
There should be a separation of ^^ ^^' between the sil- 
ver contact points, when the armature of the starting 
magnet is down. This contact should be perfect when 
the armature is up. The arm for adjusting the tension 
should not touch the wire or frame of the lamp when 
at the highest point. There should be a space of 3^2 in. 
or yi in. between the body of the clutch and the arm 
of the clutch, to allow for wear on the bearing surfaces. 

Always trim the lamp with carbons of proper length 
to cut out automatically, that is, have twice as mucn 
carbon projecting from the top as from the bottom 
holder. Always allow a space of ^ in., when the lamp 
is trimmed, from the round head screw in the rod, near 



ELECTRICITY FOR ENGINEERS 



165 



the carbvUi holder, to the edge of the upper bushing, so 
that there will be sufficient space to start the arc. 

The arcs of the 1,200 candlepower lamps should be 
adjusted to 3-64 in., with full length of carbon. Arcs of 
2,000 caadlepower lamps should be adjusted from -^■^■ 
to 3^2 ^^ when good carbons are used. 

The a, lion of a lamp that feeds badly may often be 
confounc^ed with a badly flaming carbon. The distinc- 
tion car readily be made after a short observation. 
The arc 3f a lamp that feeds badly will gradually grow 
long until it flames, the clutch will let go suddenly, the 
upper carbon will fall until it touches the lower carbon, 
and then pick up. A bad carbon may burn nicely and 
feed ev^^nly until a bad spot in the carbon is reached 
when the arc will suddenly become long and flame and 
smoke, due to impurities in the carbon. Instead of 
dropping, as in the former case, 
the upper carbon will feed to its 
correct position without touching 
the lower carbon. 

In a series arc lamp the shunt 
coil is used to regulate the voltage 
over die arc. With constant po- 
tential arc lamps this shunt coil 
is not needed, owing to the fact 
that the voltage over the lamp 
is practically constant. Fig. 94 
shows a diagram of an arc lamp 
for use on constant potential cir- 
cuits. The upper carbon is sup- 
ported by means of an iron yoke 
which forms a core to the |:wo 
solenoids M M. Current entering blading post 




FIGURE 94. 



T 



passes through the windings of these two solenoids and 



166 ELECTRICITY FOR ENGINEERS 

then through the carbons and through the resistance 
coil R to the other terminal of the lamp. The action 
of the lamp is as follows: Current passing over the 
solenoids M M is regulated by the resistance across 
the arc. This current produces an electromagnetic 
pull on the iron core and floats, magnetically, the core 
and upper carbon. When the carbons burn away at 
the crater the distance from point to point of the car- 
bons is increased and a corresponding increase in 
resistance to the flow of the current takes place. This 
reduces the flow of current around the solenoids and 
correspondingly reduces the electromagnetic pull on 
the core; the iron core and carbon fall a slight dis- 
tance by gravity. In so doing the distance at the 
crater is decreased and the flow of current increased, 
thus increasing the flow of current around the solenoids 
and drawing up the core and carbons. In this way a 
very nice equilibrium between gravity and magnetic 
pull is maintained. It will be noticed that this lamp 
has no automatic cutout as has the constant current 
arc lamp. In a series arc lamp when the carbons are 
all consumed, the automatic cutout closes the circuit 
from the positive and negative binding posts of the 
individual arc lamp, thereby maintaining a path 
through the arc lamp over which the current can con- 
tinue to flow to supply the remaining arc lamps in the 
series circuit. 

The series arc, as its name would indicate, is the 
most simple of all lighting circuits. The lamps are 
arranged so that all the current from the positive pole 
of the dynamo goes through each, and from the last on 
the conductor leads back to the dynamo. The series 
system is more generally used where it is desired to 
illuminate a large district, as in street lighting. It is 



ELECTRICITY FOR ENGINEERS 167 

also used to some extent in store lighting, although the 
"cries arc is fast being replaced with the constant 
potential arc for this purpose. 

In the low tension or constant potential arc lamp the 
use of a cutout mechanism is not necessary, because 
these lamps burn singly across the system of wiring, 
where a constant potential is maintained, and hence 
when the carbons are all consumed, current simply 
ceases to flow across them. In the open arc lamp the 
potential across the crater is usually from 45 to 50 
volts, while in the inclosed arc lamp the potential 
across the crater is from 68 to 75 volts. This is due to 
the increased resistance through the crater, because of 
the peculiar nature of the gases emitted from the 
crater burning in a condition with practically no atmos- 
phere. When such an arc lamp is connected across a 
no volt circuit, the lamp contains a resistance coil in 
the mechanism box over which the current must flow 
before producing the arc, R (Fig. 94). This resistance 
coil assists to reduce the pressure from no volts down 
to the pressure required by the arc or crater. If, for 
instance, the electromotive force across the wires 
supplying current to a low tension arc lamp is no 
volts and the pressure required to maintain the arc or 
crater is 70 volts, then the resistance coil chokes down 
the electromotive force from no to 70, or 40 volts. If 
the arc consumes 4 amperes of current then the loss is 
4 (amperes) times 40 (volts), or 160 watts. This 160 
watts is lost by heat radiating to the atmosphere from 
the wire of the resistance coil. The constant potential 
lamp is usually referred to as the low tension arc lamp. 
The high tension arc lamp generally burns with the arc 
in the open air, while the low tension lamp burns with 
the arc encased in a small glass bulb so arranged as to 



Ii18 ELECTRICITY FOR ENGINEERS 

permit the upper carbon to slide into the bulb in a 
manner that will maintain, as near as possible, a condi- 
tion whereby the arc burns in a gas containing no 
oxygen. The enclosed arc lamp has the advantage of 
burning a considerable number of hours without being 
recarboned or trimmed; but it also has the disadvantage 
that the bulb enclosing the arc turns black after burn- 
ing for some time, caused by the gases emitted from 
the arc. This renders the bulb partially opaque, 
consequently imprisoning a considerable quantity of 
useful light. Enclosed arc lamps are also operated in 
series systems, and where they are so used the objec- 
tion of loss due to the cutting down of the voltage (as 
in constant potential lamps) is Overcome. Enclosed 
lamps are also operated on alternating current systems. 

The operation of the alternating arc lamp and the 
mechanism in the lamp is very similar to that of the 
direct current arc lamp, but the magnets instead of 
being constructed of solid iron, are laminated in a 
similar manner as the system of lamination explained 
in the construction of armatures. These laminated 
cores and other parts forming the magnetic circuit 
in the arc lamp are necessary to avoid eddy cur- 
rents. The crater has neither a cup shape on the 
upper carbon nor a point on the lower carbon, because 
current flows through the crater alternately positive 
and negative with each alternation. In the alternating 
arc lamp the upper and lower carbons burn away with- 
almost equal rapidity, and the same quantity of light 
is projected upward as downward. 

In Fig. 95 is shown an arc lamp with case removed. 
The two upper coils are the coarsely wound series 
coils, while the two lower coils are the finely wound 
shunt coils. This lamp is adapte.d for an enclosed arc 



ELECTRICITY FOR ENGINEERS 



169 



bulb. The magnetically attracted cores are U shaped, 
and both cores are connected together mechanically by 
non-magnetic metal, such as brass or zinc, so that the 
magnetism set up in the shunt coils will not be affected 
by the magnetism set up by the 
series coils. This scheme is used in 
alternating current lamps, while in 
direct current lamps the cores are 
made of H shaped iron not lami- 
nated. 

In Figs. 96 to 98 are shown three 
views of series enclosed alternating 
current arc lamps of the Western 
Electric Company. 

Fig. 96. Side view of lamp, show- 
ing one series and one shunt spool, 
lever movement and adjusting 
weight. This weight is fastened 
upon a threaded rod, and the finest 
adjustment can be obtained by 
screwing the weight backward or for- 
ward. Threads can be clamped in 
position when the correct adjustment 
is obtained. 

Fig. 97. Front view of lamp, show- 
ing shunt spools, supporting resist 
ance and cutout. Note that lever 
carries no current when in normal 
working position, but that insulated bridge forms con- 
nection across two contacts, completing cutout circuit 
when in position shown in cut. 

Fig. 98. Rear view of lamp, showing series spool, 
short circuiting switch and manner of suspending dash 
pot. Note that the dash pot is inverted, allowing sucn 




FIGURE 95 



170 



ELECTRICITY FOR ENGINEERS 



dirt as may accuirul:^'': therein to fall out rather than 
in the dash pot. 

The three cuts show the manner of suspending the 
spools and their accessibility, it being possible to 
remove any spool by simply taking out the two screws 






FIGURE 96. 



FIGURE 97. 



FIGURE 98. 



which fasten it to the frame, and lifting it off the 
lower support. 

The carbons used in arc lamps are extremely hard 
and dense. They are made from a mixture of pow- 
dered gas house coke, ground very fine, and a liquid 
like molasses, coal tar, or some similar hydro-carbon, 
forming a stiff, homogeneous paste. This is molded 



ELECTRICITY FOR ENGINEERS 171 

into rods or pencils of required size and longth, or 
other shapes, being solidified under powerful hydro- 
static pressure. The carbons are now allowed to dry, 
after which they are placed in crucibles or ovens, 
thoroughly covered with powdered carbon, either lamp- 
black or plumbago, and baked for several hours at a 
high temperature. After cooling, they are sometimes 
repeatedly treated to a soaking bath of some fluid 
hydro-carbon, alternated with baking, until the product 
is dense as possible, all pores and openings having 
been filled solid. Arc carbons are often plated with 
copper by electrolysis, to insure better conductivity. 

It is said that one 2,000 candlepower arc lamp will 
light in open yards 20,000 sq. ft.; in railroad stations, 
14,000 sq. ft.; in foundries and machine shops, 5 000 
to 2,000 sq. ft. Where good, even illumination is 
oesired, it is advisable to use a greater number of 
smaller lamps evenly distributed. 



CHAPTER X 

Incandescent Lamps. As nearly every one is familiar 
with the construction of the incandescent lamp no 
detailed description will be undertaken, suffice it to 
say that the incandescent lamp comprises a carbon 
filament enclosed in a glass bulb from which the air 
has, as far as possible, been withdrawn, the carbon 
filament being soldered to the ends of small platinum 
wires entering the glass shell. Incandescent lamps can 
be burned either In series or in multiple; the multiple 
system being the most used. Series incandescent 
lamps are used to a considerable extent in the smaller 
towns for street lighting and also for the small minia- 
ture lamps burned in series on a constant potential sys- 
tem and used for decorative purposes. They are also 
used in street car lighting. 

When incandescent lamps are to be used in series, 
they should be carefully selected; there is quite a 
difference in the current consumed by d'ifferent lamps, 
even of the same make, and when they are all limited 
to the same current quite a difference in candlepower 
may be noticeable. Some will be above their rated 
candlepower and others below. 

The resistance of an incandescent lamp when cold is 
very high, varying in the ordinary i6 candlepower no 
volt lamp from 600 to 1,000 ohms. When the lamp 
becomes heated, as when current is passing through it, 
the resistance reduces considerably, being in the 16 
candlepower no volt lamp about 220 ohms. 

The current required by the various incandescent 
lamps varies considerably for lamps of the same volt- 

172 



ELECTRICITY FOR ENGINEERS 173 

age and candlepower, but a good average which can be 
used in figuring currents is Y^ ampere for a i6 candle- 
power no volt lamp and }{ ampere for the 220 volt 
16 candlepower lamp. The amount of power, in watts, 
consumed by a lamp is equal to the voltage multiplied 
by the current, or W = C x E. A 16 candlepower no 
volt lamp taking y^ ampere would consume no x 
J^ = 55 watts, while a 220 volt lamp taking ^t ampere 
would consume 220x^^ = 55 watts. It will thus be 
seen that while the current and voltage may vary, the 
amount of power consumed will be approximately the 
same for all 16 candlepower lamps. Lamps are rated 
at a certain number of watts per candle, the amount 
varying from 3 to 4 watts for 16 candlepower no volt 
lamps. The proper lamp to be used varies according 
to the conditions. While less power is consumed in 
a 3.1 watt lamp, the life of the lamp is comparatively 
shorter, so that the lamps will have to be renewed 
oftener. With a 4 watt lamp a greater amount of cur- 
rent is consumed, but the life of the lamp is longer. 
Another point of great importance in burning incan- 
descent lamps is the voltage. The table below shows 
what effect variation in voltage has on the candlepower 
and efficiency. 

An increase in voltage increases the candlepower. 
This increases the efficiency and shortens the life as 
follows: 

A lamp burning at — 

Normal voltage gives loo per cent. C. P. and consumes 3.1 Watts per C. P. 
I per cent, above normal gives 106 per cent. C. P. and consu mes 3. Watts per C P. 



2 ♦' •' 


t 


" 112 " " " 


2.9 


3 '' '• 


( (t 


- 118 " '' " 


2,8 


4 ♦* '' 


i i( 


" 12S " " 


2.7 


5 " " 


( t» 


u J32 u .. 


2.6 


6 '* " 


* ** 


.. J^Q .. .t 


2 S 



A lamp burning at normal voltage should give its 



174 



ELECTRICITY FOR ENGINEERS 



full candlepower at its rated efficiency. A 3.1 watt 
lamp burning below its voltage loses its efficiency and 
candlepower r^ follows: 
If burned- - 

1 per cent, below normal it gives 95 per cent.C. P. and consumes 3.2 Watts per C. P. 

- :; ;; ;; :; g ■; ;; :: ;: :: 3.35 ■ 



75 
70 
50 



3-6 

3.75 

U 



By referring to the table it will be seen that with the 
voltage raised 3 per cent, (on a no volt system to a 
little over 113 volts) the candlepower will increase 18 
per cent., or in other words, a 16 candlepower lamp 
would be raised to nearly 19 candlepower. At the 
same time raising the voltage will decrease the life of 
the lamp. This is show^n in the following table where, 
with an increase of 6 per cent, in the voltage, the life 
of the lamp is reduced 70 per cent. A lamp at normal 
voltage has 100 per cent. life. 

The same lamp i per cent, above normal loses i8 per cent. life. 



2 '■ 


" 30 '• 


" " " 3 " " " 


" 44 " 


4 " 


" 55 " 


" " " c; " " " 


" 62 " 


" 6 " 


" ■ " 70 " 



To obtain satisfactory results, the voltage should be 
kept constant at just the proper value. 

Considerable heat is generated in an incandescent 
lamp, so that as a general rule it is a bad plan to use 
paper shades w^hich come very close to the bulb. 
Where lamps are hung so that there is a liability of 
their coming in contact with surrounding inflammable 
material, such as in warehouses and store-rooms, it is a 
good plan to enclose the lamp in a w^ire guard. 

The following table will prove a handy reference for 
estimating the number of lamps (8 to 50 C. P.) that 
can be run per horsepower or kilow^att. The table is 



ELECTRICITY FOR ENGINEERS 



175 



figured for theoretical values, so that the actual horse- 
power or kilowatts delivered must be used, or else 
values less than those given must be used to allow for 
loss in the lines. 



Candle-power. 


Efficiency. 


Total Watts. 


Per 
Horsepower. 


Per Kilowatt. 


8 


3-5 


28 


26.6 


35.7 


8 


4 


32 


23.3 


31.2 


i6 


3 


48 


15.5 


20.8 


i6 


3.1 


50 


14.9 


20 


i6 


3-5 


56 


13.3 


17.8 


i6 


4 


64 


II. 6 


15.6 


9.0 


3 


60 


12.4 


16.6 


20 


3.1 


62 


12 


16.I 


20 


3.5 


70 


10.6 


14.2 


25 


3 


75 


9.9 


13.3 


25 


3.1 


77.5 


9.6 


12.9 


25 


3.5 


87.5 


8.5 


II. 4 


25 


4 


100 


7.4 


10 


32 


3 


96 


. 7 


10.4 


32 


3.1 


99.2 


7-5 


10 


32 


3.5 


112 


6.6 


8.9 


50 


3 


150 


4.9 


6.6 


50 


3.1 


155 


4.8 


6.4 


50 


3-5 


175 


4.2 


5-7 



The first column gives the candlepower. The second 
column gives the number of watts consumed for each 
single candlepower obtained, and is called the effi- 
ciency of the lamp. Multiply the total candlepower 
by the efficiency and you get the total number of watts 
consumed by the lamp. The fourth column shows the 
number of lamps per 746 watts, and the last coIuo^d 
the number of lamps per 1,000 watts. 

The current and watts consumed by no volt lamps 

of the different candlepowers are approximately given 

below. 

4 candlepower 0.18 amperes, 20 watts 

8 " 0.29 " 32 *• 

16 '• 0.5 •* 55 '* 

32 ** i.o " no ** 



176 ELECTRICITY FOR ENGINEERS 

The light given off by an incandescent lamp varies 
according to the position from which it is viewed. In 
some makes of lamps most of the light is given off 
directly downward, while in other lamps the maximum 
light is given off in a horizontal direction. The best 
lamp to use must be determined by the location of the 
lamp and the place where the light is required. By 
the use of suitable reflectors or shades the light can be 
thrown in any direction desired. A i6 candlepower 
lamp if placed seven feet above the floor will light up 
a floor space of lOO sq. ft., providing the walls are of a 
light color. If the walls are of a dull color, or if a 
bright illumination is desired more lamps should be 
used. Glass globes placed over the lamps reduce the 
light to a considerable extent, as is shown in the fol- 
lowing table: 

Clear glass , lo per cent. 

Holophane 12 " 

Opaline 20 to 40 *' 

Ground 25 to 30 " 

Opal , 25 10 60 " 



CHAPTER XI 

The Nernst Lamp. Very recently a new type of elec- 
tric lamp has been introduc^;d which has a few charac- 
teristics of the arc lamp and many of the characteristics 
of the incandescent lamp. It is a lamp that can be 
successfully operated only on alternating currents. 
That r^ft oi the lamp from which the light is emitted 
is called the glower. The flower performs about the 
same functions as does the filament in an incandescent 
lamp. 

In Fig. 99 a diagram of a six glower lamp is shown. 
The six glowers are shown at 6. These glowers are in 
the shape of small rods and are composed of an oxid 
which, at the normal temperature, is of very high 
resistance, the resistance being so high that practically 
no current can flow through them. When these rods 
become heated, the resistance reduces considerably, sc 
that they will conduct current. The heaters which are 
composed of a considerable length of fine platinum 
wire embedded in porcelain, are shown at 5. The 
action of the lamp is as follows: Current enters at i^ 
and being unable to flow over the glowers on account 
of their high resistance, passes to the cutout 4', then 
through the platinum wire of the heaters back to the 
other side of the cutout 4. As the platinum wire in 
the heaters becomes heated, the glowers, which are 
placed directly below them, also heat up and in time 
their resistance becomes so reduced that current will 
pass through them. The current will now pass through 
the glowers to what is known as the ballast. 7. This 

177 



178 



ELECTRICITY FOR ENGINEERS 



ballast is composed of fine iron wire and its purpose is 
to steady the current through the glower. From the 
fact that iron wire increases in resistance with increase 
of current, this wire acts as a regulator, tending to cut 




FIGUUE 9U. 



down any fluctuations in the current strength. It wiu 
be noticed that there is a separate ballast for each 
glower. From the ballast the current flows around the 
coil of wire 3. Inside of this coil is an iron core which 



ELECTRICITY FOR ENGINEERS 



179 



moves up and down, and connected to the lower end 
of this core are the cutouts 4,4'. As the glower 
becomes heated, more current is sent around this coil, 
until it becomes of such strength that the core is 
drawn in, thus opening the cutouts. All of the cur- 
rent will now flow through the glowers. The Nernst 
lamp does not operate successfully on direct current, 





FIGURE 100. 



FIGURE 101. 



due to the blackening of the glower caused by decom 
position of the platinum contacts with which they are 
connected. These lamps are made in sizes of from i 
to 30 glowers, and they consume about 88 watts per 
glower. The light resembles very closely the light 
from a Welsbach gas burner, although the green tinge 
of the Welsbach is not present. 



180 ELECTRICITY FOR ENGINEERS 

In Fig. 100 is shown the single glower lamp 
assembled, which can be inserted in an ordinary Edi- 
son socket. 

In Fig. loi the six glower lamp, with dome attached, 
IS shown. 



CHAPTER XII 

Line Testing. In the operation of electric light and 
power circuits three principal causes of trouble are 
continually encountered. These are the open circuit, 
the short circuit, the ground, and also combinations of 
these, as there is nothing which prevents the existence 
of all three defects on any line at the same time. In 
order to study these properly, let us refer to Fig. 102, 
which shows an ordinary incandescent circuit equipped 
with the necessary cutout and a switch. 

An open circuit may be caused by poor contact, or 

E . H F 



FIGURE 102. 

failure to make any contact at all, of the fuse. If this 
is the cause, the light can be made to burn by connect- 
ing the fuse terminals A and B or C and D by means 
of short pieces of wire. Such wire must, however, be 
used only for an instant to make sure of the trouble, 
and proper fuses must then be provided. Another 
method of locating an open circuit in the fuse consists 
of moistening the finger tips and placing the tips of 
two fingers of the same hand on B and D. If the fuses 
are in order, a slight shock will be felt; this method is 
applicable only on low voltage systems and must never 
be used where the voltage exceeds 250. 

181 




182 ELECTRICITY FOR ENGINEERS 

If the fuses are found all right, the next place to look 
for the cause of an open circuit is at the switch. The 
contact points of switches are often so badly burned 
or covered with dirt and grease that they do not make 
proper connection and hence the lights will not burn. 

The switch can be tested with the fingers just as we 
tested the cutout, and if the shock is felt the line is 
all right to this point. In testing the switch, be sure 
you test at the proper point (i and 2) in the figure 
which shows a switch, the blades of which cross. 
Some switches make connection straight along without 
crossing. In testing with a wire, as shown above, be 
very careful not to connect the points i and 2 at the 
switch, or you will have a short circuit. 

If the line is found alive at the far side (points I and 
2) of the switch shown, and still the lights do not burn, 
it is quite likely that there is a broken wire between 
the switch and the lamps. This break in the wire is 
not always visible, as often the wire is entirely con- 
cealed, and even when the wire is in plain view, the 
break may extend only to the copper and leave the 
outer insulation apparently perfect. 

If we are dealing with concealed wires that appear 
only where the lights are connected, we must first 
examine the connections at all such places and see 
whether they are in good order. If we find nothing 
wrong there we may proceed to locate our open circuit 
(which we shall assume to be at E) by the following 
method: In place of one of the fuses AB or CD, con- 
nect any incandescent lamp (if plug cutouts are used 
the lamp can be screwed in instead of the plug). Now 
connect a wire from i or 2 of the switch to 3 or 4 of 
the nearest lamp. 

If we happen to connect our wire from I to 4 we 



ELECTRICITY FOR ENGINEERS 183 

shall make a short circuit and the lamp at the cutout 
will burn at full candlepower, but none of the other 
lamps will burn at all. Now disconnect the test wire 
from 4 and connect it at 3; if the broken wire is at E, 
as we have assumed, all the lights will now burn in 
series wita the lamp in the cutout. If there are but 
few lights connected in the circuit, this lamp will burn 
at about haif candlepower; if there are many lamps 
connected it will come nearly to full candlepower, anc 
the lamps in the circuit will show nothing. 

If instead of an open circuit the cause of our trouble 
is a short circ^uit, it will first make itself evident by a 
burned out fuse in the cutout at AB or CD. 

A little experience will soon enable one to judge 
whether a burned out fuse is due to an overload or a 
short circuit; the damage to terminals and the evi- 
dence of burning will be much greater from a *'short" 
than from a slight overload. 

Often the current that * 'blows'' the fuse will also 
burn out the wire which caused the **short,*' so that 
the line will seem perfectly clear when a new fuse is 
inserted. 

If an inspection of the wires and apparatus does not 
reveal the location of the trouble, we may fuse up one 
side of the circuit and connect an incandescent lamp 
in place of the other fuse. If the **short" is still on, 
the lamp will burn at full candle power. 

A short circuit may consist of anything of low elec- 
trical resistance that brings the wires of opposite 
polarity into electrical connection with each other. 
Thus, if the two points, F and G, although several 
hundred feet or even yards apart, were in connection 
with gas or water piping of low electrical resistance, 
all current would flow through the piping from F to G, 



184 ELECTRICITY FOR ENGINEERS 

and there would be none to flow through the lamps. 
Short circuits are also often caused by small wires in- 
side of sockets or fixtures coming in improper contact. 
In one instance a short circuit which caused a search 
of several hours was finally located in the butt of an 
Edison base lamp, the center contact piece of which 
had been put on crooked in such a manner that when 
the lamp was screwed into its socket this center piece 
made connection with opposite poles within the socket. 

If a careful examination does not reveal the ''short" 
it will be necessary to cut the wires, say at H; if this 
clears the line so that all lamps nearer the cutout than 
H burn, the trouble must be beyond H; if not, the line 
must be cut again nearer the cutout until finally the 
exact location of the trouble is found. 

Any connection of any part of an electrical circuit to 
earth is called a ''ground," and wires so connected are 
said to be grounded. One ground on a system will 
not necessarily do much harm or interfere with the 
operation of the system. It will, however, greatly 
inCi'ease the probability of electric shocks to people 
coming in contact w^ith any part of the wiring. Also, 
if there is a ground on one side of a system, the 
appearance of a second ground on the other side of the 
system will be equal to a short circuit, if both are of 
low resistance, and probably cause the burning out of 
fuses or wires. 

If a ground is of high resistance, it may merely 
waste energy through leakage of current; or it may 
cause slow destruction of a wire or sometimes a gas or 
water pipe by electrolytic action. Aside from direct 
contact with metal parts of buildings, the most prolific 
cause of grounds is found in dampness. 

Grounds may be located by means of the VVheatstone 



ELECTRICITY FOR ENGINEERS 



185 



bridge, magneto or a common bell and battery. After 
removing the fuses from the grounded part of the 
system, connect one side of the apparatus to a good 
ground, such as a water pipe, and the other side to the 
system. Proceed in the same way as explained for 
short circuits; that is, cut the lines until the ground is 
located, or the line shows clear. Where the wiring is 
concealed and there are a number of switches control- 
ling chandeliers, grounds can very often be located by 
switching off one fixture at a time, for when the 
grounded fixture is switched off the line will show 
clear. 

To facilitate the discovery of grounds as soon as they 
come on, most switchboards are equipped with ground 
detectors of some kind. 

The cheapest and easiest to install of these consists 
of two lamps in series, as shown in Fig. 103. So long 



JA 



+ 



^ 




FIGURE 103. 



as both sides of the system are clear of grounds, the 
lamps will both burn at equal candlepower (rather dim) 
no matter whether the buttom C be pressed or not. 
But should a ground come on the -f wire, say at B, and 
the button C be then pressed, the lamp 2 will be 
deprived of current and lamp I will burn at full candle- 
power. In such a case the current passes from the 
-*- wire to the ground B, through the ground to C, 



186 



ELECTRICITY FOR ENGINEERS 



button C and lamp i to the — wire. Should a ground 
come at A, lamp i would be cut out and 2 wourd 






w 



i 



DH 




ao-i 



^ 



to 



o 
o 



* + 



burn at full candlepower. The great disadvantage of 
the lamp ground detector lies in the fact that it is not 
very sensitive; that is unless the ground is of quite 



ELECTRICITY FOR ENGINEERS 



187 



low resistance the difference in the brilliancy of the 
lamps will hardly be noticeable. 

A much more satisfactory arrangement is that shown 
in Fig. 104, where a voltmeter is connected for that 
purpose. With the two single pole switches A and B 
in the position shown, the voltmeter indicates the 
pressure of the dynamo; if B is thrown over, the 
current from the -f wire passes through the voltmeter 
to the ground, and if there is a ground on the - wire it 
will indicate it. If B is thrown back and A over, a 




^ ^ 



I 



n 



ff 



ti 



FIGURE 105. 

ground on the + wire will be indicated. If the system 
is perfectly clear, the voltmeter will indicate nothing 
with either one of the switches thrown over. This test 
of lines and circuits should be quite frequently made. 

Testing Efficiency of Dynamos and Motors. The simplest 
means of testing the efficiency of motors is shown in 
Fig. 105. 

This is known as the Prony brake, and consists of a 
pair of clamps arranged for thumb screws and fastened 
to the pulley of the motor, and a set of scales. 

We will assume that we are testing the efficiency ot 



188 ELECTRICITY FOR ENGINEERS 

a motor. We will arrange the clamps over the pulley 
as shown in the figure and on the long end of the 
clamp we will arrange a bolt, from which we may 
impart the pressure obtained to the platform of a pair 
of scales. In the circuit supplying the motor with cur- 
rent we will connect an amperemeter and a voltmeter. 
We will now start the motor and press down on the 
clamps by means of the thumb screw, until the 
mechanical energy expended is sufficiently high to 
cause the desired consumption of current shown by the 
amperemeter at the pressure shown by the voltmeter. 
With a tachometer or speed indicator we will find the 
number of revolutions of the motor per minute. When 
this has been done, we will take the weights on the 
scales and balance the pressure brought down on the 
platform. Now stop the motor. The weight indi- 
cated by the scales is that weight which the motor 
would have revolved through a circle, the radius, or 
half the diameter of which is the distance from the 
center of the motor shaft to the center of the bolt 
pressing on the scale platform, Fig. 105. To find the 
horsepower exerted, multiply the distance between the 
bolt and the armature shaft by 2. This will be the 
diameter of the circle described. Multiply this by 
3.1416. This will be the circumference of the circle 
described. Multiply this by the number of pounds 
indicated by the scales, multiply this by the number of 
revolutions per minute, and divide the answer by 
33,000. 

Suppose yqur amperemeter registered 50.9 amperes 
and your voltmeter registered no volts. This would 
be 50.9 X no = 5,599 watts consumed. Divided by 746 
watts, the electrical horsepower would be 7^ horse- 
power consumed. 



ELECTRICITY FOR ENGINEERS 189 

Suppose the dynamometer proved that you obtained 
six actual mechanical horsepower. Then 6 divided by 
7>^ would be 80 per cent, efficiency which the motor 
would have for changing electrical energy into mechan- 
ical energy. 

To test the efficiency of a dynamo we must first find 
how much power is being delivered to it by the engine. 
This is done in the usual manner by means of the indi- 
cator, etc. Having obtained this, it is simply neces- 
sary to connect an ammeter and voltmeter and, taking 
simultaneous readings of both, find the power given 
out by the dynamo by multiplying together the volts 
and amperes. 

As an example, suppose we have found that our 
engine is delivering 40 H, P. while we are obtaining 
from our dynamo 200 amperes at no volts pressure. 
200x110 divided by 746 will give us the electrical 
energy we are receiving; in this case a trifle less than* 
29.5 H. P. To find the efficiency of the dynamo we 
divide the power received from the dynamo by that 
delivered to it by the engine, 29.5 divided by 40 equals 
.737, which is the efficiency of this dynamo. When 
testing dynamos it is usual to provide an artificial load 
which can be kept constant. Large metal plates^ 
preferably copper, are connected to the positive and 
negative mains of the dynamo and immersed in a 
barrel of water. The quantity of current that will flow 
from one plate to the other can be regulated by dis- 
solving more or less salt in the water and by immers- 
ing the plates more or less and also by bringing them 
closer together. The greater the surface of the plates 
immersed in the water and the nearer they are brought 
together, the greater will be the current. Be very care- 
ful and do not let the plates touch each other. Before 



190 



ELECTRICITY FOR ENGINEERS 



accepting a new dynamo a test run of twenty-foui 
hours at full load is usually made and the water rheo- 
stat need be used only to keep the load constant when 
lights are switched on or off. 

Photometer. The amount of light given off by an 
incandescent lamp is measured in candlepower. To 
determine the candlepower of a lamp, an apparatus 
known as the photom.eter is used. Fig. io6 shows a 
diagram of what is known as the Bunsen photometer. 
S is a scale divided into inches, meters, or any suitable 
divisions, at one end of which is placed a standard 
lamp and at the other end the lamp to be measured. 




FIGURE 106. 



A small screen, made of white paper having a grease 
spot in the center, is mounted on a stand so that it can 
be moved along the scale. To operate the instrument, 
move the screen to such a point that the grease spot 
becomes invisible from either side. The two candle- 
powers are now to each other as the squares of their 
distances from the screen. For instance, suppose the 
lamp A is a standard i6 candlepower lamp and at the 
point where the grease spot is invisible the distance 
from B to the screen is 20 in., and from A to the 
screen 40 in., then B is to A as 20 squared is to 40 
squared, or as 400 is to 1,600 or one-fourth as 
great; therefore B is a 4 candlepower lamp. Care must 



ELECTRICITY FOR ENGINEERS 



191 



be taken that the two lamps are burning at just the 
proper voltage, otherwise the comparison will not be 
accurate. Instruments of the kind just described are 
made in a variety of different patterns, but their prin- 
ciple remains the same. Candlepowers may also be 
compared by a method known as Rumford's. Take a 
pencil or other opaque rod and place it in front of a 
white piece of paper or light-colored wall. Now place 




FIGURE 107. 

in front of it, but separated so that there will be two 
separate shadows cast, the two lamps to be compared. 
By moving one of the lamps away from, or closer to, 
the screen, at some point the two shadows will become 
of the same density. Now measure the distances of the 
two lamps from the screen, and their candlepowers 
will be to each other as the squares of the distances; 
(Fig. 107). 



192 ELECTRICITY FOR ENGINEERS 

If the current consumed by a lamp and the voltage 
maintained at its terminals are measured by an amme- 
ter and voltmeter, as shown in Fig. io6, we need only 
find the watts (current times volts) and divide by the 
candlepower to find the efficiency of the lamp. If, for 
instance, the 4 candlepower lamp B is taking ^ ampere 
at no volts, we have 18^ watts expended on it; this 
divided by the candlepower 4 shows an efficiency of 
4y\ watts per candle. 



CHAPTER XIII 

Storage Batteries. The storage battery is often 
referred to as an accumulator. An accumulator is an 
appliance for storing electricity. It depends upon the 
chemical changes undergone by certain substances 
when subjected to the action of an electric current. 
Strictly speaking, it is not correct to say that electri- 
city is stored in an accumulator, although as far as 
external results is concerned such appears to be the 
case. What it really does is this: The current flowing 
into the accumulator produces a gradual chemical 
change or decomposition of the active elements of 
which the battery is constructed. This change con- 
tinues to take place as long as the charging current is 
applied. This is known as electrolytic action. As soon 
as the current ceases, so also does the chemical decom- 
position of the elements cease, and if the terminals be 
then connected by a wire, a reversal of the chemical 
process commences. Particles gradually reform them- 
selves into original chemical combinations, and by so 
doing produce a current of electricity which flows in 
opposite direction to that originally used for charging. 

An early form of accumulator, though more of 
experimental than practical interest, was Grove's gas 
battery. This was composed of a series of cells, each 
cell comprising two tubes, closed at the upper ends, 
and dipping down into a glass jar containing acidu- 
lated water. Each tube had a platinum wire fused into 
the closed end, from which a strip of platinum foil 
extended downwards into the liquid. The outer ends 

193 



194 ELECTRICITY FOR ENGINEERS 

of the platinum wires were provided with terminals, by 
means of which several of these cells were connected 
together. A charging current was then applied and 
resulted in the gradual decomposition of the water in 
the various glass jars. Hydrogen collected on one of 
the platinum plates in each of the cells and oxygen on 
the other. If after a short time the charging source 
was disconnected from the wires joined to the outer 
terminals of the cells and a galvanometer substituted, 
it was found that a current would then flow in the 
reverse direction until all the separated hydrogen and 
oxygen gases had recombined to form water again. 

From a practical point of view the gas battery was 
deficient, inasmuch as it would only supply current for 
a very short time, and several workers set themselves 
the task of contriving an arrangement to obviate this 
defect. The most successful of these early workers 
was Plante, and he found in the course of his experi- 
ments that the best results were to be obtained by 
using lead plates or electrodes in a dilute solution of 
sulphuric acid. He made a cell by taking two long 
strips of sheet lead, placed one over the other with 
pieces of insulating material between, 'and coiling 
these up into spiral form. These plates were provided 
with separate terminals and were placed in a jar con- 
taining a solution of sulphuric acid. The action of the 
charging current was to decompose the water in the 
solution, the oxygen combining with the metal of the 
positive plate and thus forming peroxide of lead, 
whereas the hydrogen was simply deposited on the 
negative plate and there remained in gaseous form. 
On discontinuing the charging current, the hydrogen 
combined with the oxygen in the solution to form 
water again, while the peroxide of lead was deoxidized, 



ELECTRICITY FOR ENGINEERS 195 

the lead remaining on the surface of the plate as 
spongy lead» and the oxygen reentered the solution to 
compensate for the oxygen which was extracted there- 
from by the hydrogen in forming water. Plante found 
that this method of construction enabled him to get an 
,'Jectromotive force of from 2 to 2.5 volts, as against 
1.47 volts given by Grove's gas battery. 

Planters experiments did not, however, terminate 
with this achievement, and he next introduced a 
method for considerably increasing the available 
metallic surface of the electrodes. This plan is known 
as "forming" the plates, and consists of repeating for 
a considerable time the following series of operations: 
(i) charge the accumulator, (2) discharge ditto, (3) 
recharge, but with the charging current entering in the 
reverse direction, (4) again discharge. This series of 
reversals in charging and discharging, if kept up for 
several days, has the effect of causing the lead plates 
to become very porous or spongy in character, and, 
therefore, by reason of the additional surface of con- 
tact between electrolyte and electrode thus provided, 
enables the cell to retain a much greater charge than 
it would otherwise. 

It is not difficult to see that this work of forming 
i:: of a somewhat tedious and expensive character, and 
with the object of reducing this process to a minimum, 
another inventor, Faure, conceived the idea of using 
plates coated with a paste of lead-oxide, a plan which 
made it possible to use an accumulator with success 
after being charged only two or three times. When first 
introduced, some difficulty was found in making the 
lead-oxide paste adhere properly to the plates, and 
various means were devised to overcome this drawback. 
Scratching and indenting the lead plates was tr'ed, 



196 ELECTRICITY FOR ENGINEERS 

but this was ultimately superseded by the plan of 
making perforated plates in the form of grids, tho 
paste being pressed into the perforations. With vari- 
ous slight modifications, in the shape of perforations, 
this device has been found to answer exceedingly well, 
and is now very generally adopted. 

When an accumulator is freshly charged, it would be 
found to have an electromotive force of about 2.25 to 
2.5 volts, but after being used a short time this falls to 
about 2 volts, at which figure it remains until the cell 
is nearly exhausted. For many purposes, however, a 
higher voltage than this is required, and it then 
becomes necessary to have several cells joined in 
series, so as to give a total voltage equal to the 
number of cells multiplied by 2. Thus 20 cells of 2 
volts each, if joined in series, would give an electro- 
motive force of 40 volts; 50 cells would give 100 volts, 
and so on. 

The quantity of current which a cell will accumulate 
or store depends upon the area of its plates; the larger 
the plates the greater the capacity of the cell, and the 
higher the permissible rate of discharge. As it is not 
always convenient to use very large plates where great 
capacity is required, the same result may be obtained 
by using a number of small plates to increase the 
available plate surface, but in such cases the plates 
must be connected in parallel. That is, the positive 
plates must all be connected to one terminal, and the 
negative plates all to the other terminal, thus forming 
practically two plates divided into a number of 
branches. 

The capacity of an accumulator is usually measured 
in ampere hours. Thus an accumulator which will 
discharge a current of ten amperes for one hour, or of 



ELECTRICITY FOR ENGINEERS 



197 



five amperes for two hours, or of one ampere for ten 
hours, is said to have a capacity of ten ampere hours. 
As a general rule, it may be estimated that an accumu- 
lator has a capacity of six ampere hours for each 
square foot of positive plate surface. 

For charging storage batteries the shunt dynamo is 
generally used, and the voltage must be kept as nearly 
constant as possible. Fig. io8 shows a very simple 
installation where the battery is intended to be charged 
during the running tim^. of the dynamo and to carry 
the lights during such time as the dynamo is not in 




®=^- 


-J 


m 


'^(TK) ]a ■■■■■■■ 


llllll[i 
11 ijl 1 II 


II 


1 


L _ 

II 


1 1 


II 


III 


II 


II 


III llllll 



FIGURE 108. 



action. The ammeter A, in the battery line, should 
be of a kind which indicates the direction of the cur- 
rent passing through it. The rheostat R is used to 
regulate the charging current and the voltmeter V is 
connected so that either the voltage of the dynamo or 
the battery may be taken. In addition to this volt- 
meter a low reading meter should also be provided to 
test single cells. An automatic circuit breaker is also 
often provided to open the circuit should the current 
through it flow in the wrong direction. Should, for 
any reason, the voltage of the dynamo fall below that 



198 ELECTRICITY FOR ENGINEERS 

of the battery while charging, the battery would begin 
to discharge through the dynamo. Where it is import- 
ant that the voltage supplied by the battery shall be 
at the same voltage as that supplied by the dynamo, a 
"booster" is employed to help charge the battery. 
Such a booster increases the electromotive force at 
the terminals of the battery sufficient to allow it to be 
charged to the full pressure of the dynamo. In setting 
up and charging storage batteries, detailed instructions 
should be obtained from the makers and rigidly 
followed. 



CHAPTER XIV 

Electrolysis. Electrolysis is chemical decomposition 
effected by means of the flow of an electric current. 
By electrolytic action it is possible to deposit metals, 
such as gold, silver, nickel, etc., over the exterior 
surface of other metals. This process is ordinarily 
called nickel plating, gold plating, etc., and is carried 
on by means of tanks in which there are liquids hold- 
ing in solution some of the various metallic salts. By 
placing over these tanks a bar or number of bars made 
of brass or copper, we may hang articles from these 
bars by means of wires, so that they are submerged in 
the solution. Now by using a dynamo whose output 
is low in pressure or electromotive force and high in 
quantity or amperes, and connecting the positive or 
outgoing terminal of this machine to a piece of metal, 
such as copper, nickel, gold, or silver, and submerging 
this metal in the liquid contained in the tank, the flow 
of current from this piece of gold or silver into the 
liquid or bath will carry with it, by electrolysis or 
electrolytic action, some of this gold or silver and 
deposit it on the articles suspended in the liquid, from 
the brass or copper bars to which the negative terminal 
of the plating dynamo is connected. The use of the bath 
containing metallic salts reduces the resistance from 
the metal to be deposited on the articles that are to be 
plated, which are the negative electrodes. This effects 
an equal deposit of metal over the entire surfaces 
being subjected to the electrolytic or plating action. 

Where it is desired to cover such metals as steel or 

199 



200 ELECTRICITY FOR ENGINEERS 

iron with silver or gold, it becomes necessary to subject 
the articles to De plated to what is called a striking 
bath. This striking bath consists of a system of elec- 
trolytic action as above described, where copper is first 
deposited over the surfaces of iron or steel. The more 
precious metals will distribute themselves over this 
copper surface more uniformly and in a finer grained 
manner than if the article had not been copper plated 
first. After the plated article has had sufficient metal 
deposited on its surface, it is put through a buffing and 
polishing process for its final finish. 

Electrolysis has also been applied where it is desired 
to reclaim the precious metals from ores without smelt- 
ing them. This method consists of immersing the ore 
in tanks filled with a solution. The ore receives cur- 
rent from the positive element of a dynamo through 
the liquid solution, and the metal in the ore is depos- 
ited on the negative plate in the vat, which is con- 
nected to the negative terminal of the dynamo. Thus 
by employing a process similar to electro plating it is 
possible to extract the metal from the ores in almost 
its pure state from the negative plate. The solution 
mentioned is water in which various kinds of metallic 
salts have been dissolved which bear a chemical rela- 
tion to the metals to be extracted. 

This short description will assist in explaining how 
electrolytic action takes place in water and gas pipes 
buried under the surface of the ground, when, for 
instance, electric railroads, operated in the vicinity 
are not properly constructed. In the construction of 
an electric street railroad or trolley line the generators 
are connected to the trolley wires usually at the posi- 
t'^^^ terminals of the dynamos. 

The current passes from the trolley line through the 



ELECTRICITY FOR ENGINEERS 201 

car to the rails and back to the negative pole of the 
dynamo. If the rails are not of sufficient carrying 
capacity, or if there is a pipe line of better carrying 
capacity near the rails, it is quite certain that some of 
the current will be carried by the pipes. Wherever 
the current leaves a pipe it carries some of the metal 
with it, and if there is much current a hole will soon 
be eaten into the pipe. As the pipes are mostly 
covered with rust, which is a partial insulator, the 
current will be most likely to enter and leave the pipe 
at some point which is comparatively bright and the 
electrolytic action will be concentrated at such points. 

Heating by Electricity. The electric heater is simply 
a coil of wire through which enough current is caused 
to flow to produce quite an appreciable amount of 
heat. In the use of resistance coils for nearly all elec- 
trical purposes the function of the resistance coil is to 
cut down the flow of current required at some point, as 
for instance, where a resistance coil is used as a start- 
ing box on a motor. The flow of current across or 
through such a coil or coils, will produce heat, and 
shows one way in which electric power can be con- 
verted into heat. Another instance, if a contact is 
poorly made, the resistance to the flow of current 
offered by this contact produces heat and a consequent 
loss of watts. The voltaic arc in an arc lamp is 
another instance where resistance to the flow of current 
is interposed in the circuit and consequently produces 
heat. 

The incandescent lamp is another instance where 
resistance is the cause of the production of heat, but, 
of course, in both the arc and incandescent light, the 
result desired is a maximum amount of light with a 
minimum amount of heat. 



202 ELECTRICITY FOR ENGINEERS 

If we were to construct a coil of small wire, whose 
total resistance would be the same as that of another 
coil of large wire, it would be found that the coil of 
small wire would contain much less wire than the coil 
of large wire, both resistances being the same in ohms. 
Now if both these coils were connected across a circuit, 
we will say of no volts, the same amount of current 
would flow over both the coils, because their resist- 
ances are alike, but the smaller coil would get quite 
hot, while the larger coil would perhaps be just 
slightly warmed. The number or quantity of heat 
units gi en out by both coils are the same. The sur- 
face from which these heat units pass out into the 
atmosphere is much less in the smaller coil than in the 
large one, hence the smaller coil gets quite hot, some- 
times even red hot. If we were to permit current to 
flow over this small coil and maintain its temperature 
at a low red heat, it would in time become oxidized by 
the chemical action of the oxygen in the air. To pre- 
vent this oxidization we may imbed this small coil in 
a porcelain cement, and after it has been properly 
imbedded in this cement we will put the entire coil 
and cement through a baking process, making the 
cement quite hard and sealing the wire coil from the 
influence of the oxygen in the atmosphere. Then 
we can take this coil so constructed and produce 
heat in a flat iron, or in a stove, in a curling iron, 
soldering iron, and in fact anywhere. The coil being 
so hermetically sealed it can also be used in chafing 
dishes, tea kettles, water urns, glue pots, etc. The 
principle of producing heat by electricity remains the 
same no matter where or how it is applied, the only 
difference necessary being in the form given to the 
heater coils. 



ELECTRICITY FOR ENGINEERS 203 

Heating by electricity is quite an expensive and 
uneconomical proposition, and an idea can be obtained 
as to the quantity of current necessary to do electric 
heating, when we consider that in very cold weather it 
requires nearly as much power to operate the heat'^rs 
in a street car system as it does to propel the cars. 



CHAPTER XV 

LigMiiing Arresters. Lightning arresters are needed 
I I overhead, outdoor lines only. The simplest form 
< f lightning arrester consists of two bare metal plates 
et very close together, but under no circumstances 
illowed to touch each other. (See Fig. 109.) One of 
these plates is connected to the overhead line and the 
other to the ground. 

A sudden flow of current meets with an enormous 
opposition when it encounters the coils of a large 
electro magnet. Although the resistance of the air 
space between the two plates forming the lightning 
arrester may be several millions of ohms, it is far 
easier for the current to jump this air space in such a 
very short time as is taken up by a lightning discharge 
than it would be to force its way around the coils of 
the m.agnet. The reason for this is, that a current of 
electricity flowing through the coils of an electro mag- 
net creates magnetism or lines of force. These lines 
of force cut through the coils on the magnet and in 
that way tend to produce a counter current, or counter 
electromotive force, which, for a very short time, is 
almost equal to the electromotive force creating it. 
Were the current flow to continue for any appreciable 
time this counter electromotive force would disappear 
entirely as soon as the magnetism reached its final 
strength. 

In order, therefore, to facilitate as much as possible 
a lightning discharge towards the ground and away from 
the machinery and buildings, the wires leading from 

204 



ELECTRICITY FOR ENGINEERS 



205 



the arresters to the earth should be run in as straight a 
line as possible and be kept well separated from metai 
parts, especially iron of the building. Under no cir- 



TO 
LINE 



^ 



Wvwwwwwwv 

AAA/XAAAAAAAAAAAA 



TO 
GROUND 



FIGURE 109. 



cumstances should the ground wire be run in an iron 
pipe, nor should lead covered wires be used. 

With the simple lightning arrester shown above there 
is great liability of the cnrrent from the dynamo fol- 
lowing the arc caused by the lightning discharge to 



206 



ELECTRICITY FOR ENGINEERS 



ground, and, as there must be two arresters, one on each 
side of the dynamo, this amounts almost to a short 
circuit and is very likely to put the dynamo out of 
service. Should such an arc continue for a few min- 
ites, it may fuse the plates of the arrester. The arc 
v;an readily be extinguished by blowing it out or caus- 
ing a strong blast of air to strike it. 

To prevent trouble of this kind the Thomson light- 




FIGURE 1 10. 



ning arrester, shown in Fig. no, was devised. This 
jnsists of the two diverging metal plates shown at 
the top of the figure, one of which is connected to the 
earth and the other to the line to be protected and an 
electro magnet, as shown. The current from the 
dynamo traverses the coils of the electro magnets. 
The action is as follows: When a lightning discharge 
through the arrester takes place, it forms an arc 



ELECTRICITY FOR ENGINEERS 207 

between the lower points of the plates above the mag- 
nets. These plates are very close together at the 
bottom. Now the electric arc is always strongly 
repulsed by a magnet, and hence the arc formed is 
forced upward where the plates diverge, and the space; 
becomes too great for it to be maintained and it is 
then broken. The arc is virtually blown out by thi. 
magnetism. 



EXAMINATION 
QUESTIONS AND ANSWERS 



INTRODUCTION 



The development of the science of steam engineering 

and the continually increasing demand for more power 
for manufacturing purposes and for transportation, both 
on land and sea, have in these modern times resulted in 
the creation of power plants, which are truly marvelous 
in their details when compared with the steam machinery 
of forty years ago. Even the last twenty years have 
witnessed tremendous developments along these lines, and 
we may imagine the effect it would have upon an 
engineer, who twenty years ago was counted as first class 
in his business, but who, having taken a Rip Van Winkle 
sleep of twenty years, is suddenly awakened and finds him- 
self set down in the engine room of a first-class ocean 
steamer, or in the midst of one of our modern up-to-date 
power plants. The facts are, he would have hard work 
to recognize his surroundings. Even the steam gauges 
would indicate a pressure of 150 to 175 pounds more per 
square inch than did the old-time gauges. Therefore, in 
view of the remarkable improvements in steam machinery 
which have been made and are continually being made, it 
certainly behooves engineers to do their utmost to keep 
step with the march of progress. The author has endeav- 
ored, in the following pages, to place before his readers 
information in a catechetical form which will be found to 
cover all of the various details appertaining to the opera- 
tion of modern steam plants, both stationary and marine. 

C. F. S. 



CHAPTER I 

STEAM, HEAT, COMBUSTION, AND PUBLS 

Ques. 1. — What is steam? 

Ans. — Steam is vapor of water. 

Ques. 2. — At what temperature will water evaporate 
(boil) in the open air at sea level? 

Ans. — 212 degrees Fahrenheit. 

Ques. 3. — If 1 cubic foot of water is evaporated at 
212 degrees into steam at atmospheric pressure, how 
many cubic feet of steam will there be? In other words, 
what will the volume of the steam be? 

Ans. — 1,646 cubic feet. 

Ques. 4. — Then what is the relative volume of steam 
at atmospheric pressure, and the water from which it was 
evaporated at 212 degrees? 

Ans.— 1,646 to 1. 

Ques. 5. — What is the relative volume of steam at 
200 pounds gauge pressure, and the water from which it 
was generated? 

Ans.— 132 to 1. 

Ques. 6. — What is meant by the terms atmospheric 
pressure, gauge pressure, and absolute pressure, as 
applied to steam and other gases? 

Ans. — The pressure in pounds exerted by the steam, 
or gas, on each square inch of the interior surface of the 
containing vessel, tending to rupture it. 

7 



8 



QUESTIONS AND ANSWERS 



Ques. 7. — What is vacuum? 

Ans. — The absence of all pressure in the interior of a 
vessel. 

Table 1, which follows, shows the physical properties 
of saturated steam from a perfect vacuum up to 1,000 
pounds absolute pressure. It will be found convenient 
for reference. 



TABLE I 

Properties of Saturated Steam 



>^ 


.G 




Total 


Heat 






6 


t 


S3 




a 




above 


32° F. 


^ 


B 


.SS 


' 


U 












3 
'0 
> 
a; 
> 

a; 


M 






5 m 


S en 
I— 1 


Xi . 


29.74 


.089 


32. 


0. 


I09I.7 


1091.7 


208,080 


3333.3 


.0003 


29.67 


.122 


40. 


8. 


1094. 1 


1086.1 


154,330 


2472.2 


.0004 


29.56 


.176 


50. 


18. 


1097.2 


1079.2 


107,630 


1724.1 


.0006 


29.40 


.254 


60. 


28.01 


1100.2 


1072.2 


76,370 


1223.4 


.0008 


29.19 


.359 


70. 


38.02 


1103.3 


1065.3 


54»66o 


875.61 


.0011 


28.90 


.502 


80. 


48.04 


1106.3 


1058.3 


39,690 


63=;. 80 


.0016 


28.51 


.692 


90. 


58.06 


llOg.4 


I05I.3 


2Q,290 


469.20 


.0021 


28.00 


.943 


100. 


68.08 


1112.4 


1044.4 


21,830 


349^70 


.0028 


27.88 


I. 


102. 1 


70.09 


III3.I 


1043.0 


20,623 


334.23 


.0030 


25.85 


2. 


126.3 


94.44 


1120.5 


1026.0 


10,730 


I7>23 


.0058 


23.83 


3. 


141. 6 


109.9 


II25.I 


IOI5.3 


7,325 


118.00 


.0085 


21.78 


4. 


153. 1 


121. 4 


1128.6 


1007.2 


5,588 


89.80 


.0111 


19.74 


5. 


162.3 


130.7 


II3I.4 


1000. 7 


4,530 


72.50 


.0137 


17.70 


6. 


1 70. 1 


138.6 


II33.8 


995.2 


3,8i6 


61.10 


.0163 


15.67 


7. 


176.9 


145.4 


II35.9 


990.5 


3,302 


53.00 


.0189 


13.63 


8. 


182.9 


151.5 


1137.7 


9S6.2 


2,912 


46.60 


.0214 


11.60 


9. 


188.3 


156.9 


II39.4 


982.4 


2,607 


41.82 


.0239 


9.56 


10. 


193.2 


161.9 


II4O.9 


979.0 


2,361 


37.80 


.0264 


7.52 


II. 


197.8 


166.5 


II42.3 


975.8 


2.159 


34.61 


.0289 


5.49 


12. 


202.0 


170.7 


II43.5 


972.8 


1,990 


31.90 


.0314 


3.45 


13. 


205.9 


174.7 


1 144. 7 


970.0 


1,846 


29.60 


.0338 


r.41 


14. 


209.6 


178.4 


1145.9 


967.4 


1,721 


27.50 


.0363 


0.00 


14.7 


212.0 


180.9 


1 146. 6 


965.7 


1,646 


26.36 


.0379 



STEAM, HEAT, COMBUSTION, AND FUELS 

Table i — Conti?med 





0) 




Total Heat 




D 


s 







3 fl 
in'—' 


^ 


Above 


32«F. 


^ 
?, ^ 


s 


■tl 


£i 








^ to 


I ^ 


(D +-> 


'0 

> 










7i V- 




^J^ 


ri 


> 


s? 


"1 


^^ 


14 


Q 






- X 






0^ 


OhJ 


< 










3^ 


M 




0.3 


15 


213.3 


181. 9 


1146.9 


965.0 


1,614 


25.90 


.0387 


1.3 


16 


216.3 


185.3 


1147.9 


962.7 


1,519 


24.33 


.0411 


2.3 


17 


219.4 


188.4 


1148.9 


960.5 


1,434 


23.00 


.043c: 


3.3 


18 


222.4 


191.4 


1149.8 


958.3 


i,35Q 


21.80 


.045Q 


4.3 


19 


225.2 


194.3 


1150.6 


956.3 


1,292 


20.70 


.0483 


5.3 


20 


227.9 


197.0 


1151.5 


954.4 


1,231 


19.72 


.0507 


6.3 


21 


230.5 


199.7 


1152.2 


952.6 


1,176 


18.84 


.0531 


7.3 


22 


233.0 


202.2 


1153.0 


950.8 


1,126 


18.03 


.0555 


8.3 


23 


235.4 


204.7 


1153.7 


949-1 


1,080 


17.30 


.0578 


9.3 


24 


237.8 


207.0 


1154.5 


947.4 


1,038 


16.62 


.0602 


10.3 


25 


240.0 


209.3 


1155.1 


945.8 


998 


16.00 


.0625 


11.3 


26 


242.2 


211. 5 


1155.8 


944.3 


962 


15.42 


.0649 


12.3 


27 


244.3 


213.7 


1156.4 


942.8 


929 


14.90 


.0672 


13.3 


28 


246.3 


215.7 


1157.1 


941.3 


898 


14.40 


.0696 


14.3 


29 


248.3 


217.8 


1157.7 


939.9 


869 


13.91 


.0719 


15.3 


30 


250.2 


219.7 


1158.3 


938.9 


841 


13.50 


.0742 


16.3 


31 


252.1 


221.6 


1158.8 


937.2 


816 


13.07 


.0765 


17.3 


32 


254.0 


223.5 


II 59.4 


935.9 


792 


12.68 


.0788 


18.3 


33 


255.7 


225.3 


1159.9 


934.6 


769 


12.32 


.0812 


19.3 


34 


257.5 


227.1 


1 160. 5 


933.4 


748 


12.00 


.0835 


20.3 


3.^ 


259.2 


228.8 


1161.0 


932.2 


728 


11.66 


.0858 


21.3 


36 


260.8 


230.5 


1 16 1. 5 


931-0 


709 


11.36 


.0880 


22.3 


37 


262.5 


232.1 


1162.0 


929.8 


691 


11.07 


.0903 


23.3 


38 


264.0 


233.8 


1 162. 5 


928.7 


674 


10.80 


.0926 


24.3 


39 


265.6 


235.4 


1162.9 


927.6 


658 


10.53 


.0949 


25.3 


40 


267.1 


236.9 


1163.4 


926.5 


642 


10.28 


.0972 


26.3 


41 


268.6 


238.^ 


1163.9 


925.4 


627 


10.05 


.0995 


27.3 


42 


270.1 


240.0 


1164.3 


924.4 


613 


9-83 


.1018 


28.3 


43 


271.5 


241.4 


1164.7 


923.3 


600 


9.61 


.1040 


29.3 


44 


272.9 


242.9 


1165.2 


922.3 


587 


9.41 


.1063 


30.3 


45 


274.3 


244-3 


1165.6 


921.3 


575 


9.21 


.1086 


31.3 


46 


275.7 


245.7 


1166.0 


920.4 


563 


9.02 


.1108 


32.3 


47 


277.0 


247.0 


1 166. 4 


919.4 


552 


8.84 


.1131 


33.3 


48 


278.3 


248.4 


1166.8 


918.5 


541 


8.67 


.1153 


34.3 


49 


279.6 


249.7 


1167.2 


917.5 


531 


8.50 


.1176 


35.3 


50 


280.9 


251.0 


1167.6 


916.6 


520 


8.34 


.1198 


36.3 


51 


282.1 


252.2 


1168.0 


915.7 


511 


8.19 


.1221 


37.3 


52 


283.3 


253.5 


1168.4 


914.9 


502 


8.04 


.1243 



10 



QUESTIONS AND ANSWERS 



Table i — Contimied 





c 




Total Heat 







S 


•8 


£g* 


^i 




above 


32«F. 


-t-> 








fo CO 






<3J ^ 








3 
> 

a; 




,,-^ 




5 ^ 


1 ^ 

rt .4-1 
•:: 


5i 




-^ 




^ g 


^^§ 


Fs 


.— 







3 Cfi 


1-^ 


G 


^"i 


^""rt 


- X 


rt 


^ 


^^ 


oa 


^.-1 




t: a; 


•^ 




Ph 


^I'o 




< 




a K 


c K 








^ 


38.3 


53 


284.5 


254.7 


I168.7 


Q14.0 


492 


7.90 


1266 


39-3 


54 


285.7 


256.0 


I169.1 


913.1 


484 


7.76 


1288 


40.3 


55 


286.9 


257.2 


1 169. 4 


912.3 


476 


7-63 


I31I 


41-3 


56 


288.1 


258.3 


T169.8 


911-5 


468 


7.50 


1333 


42.3 


57 


289.1 


259-5 


1 1 70. 1 


910.6 


460 


7.38 


1355 


43.3 


53 


290.3 


260.7 


1170.5 


909.8 


453 


7.26 


1377 


44.3 


59 


291.4 


261.8 


1170.8 


909.0 


446 


7.14 


1400 


45.3 


60 


292.5 


262.9 


II71.2 


90S. 2 


439 


7.03 


1422 


46.3 


61 


293.6 


264.0 


1171-5 


Q07.5 


432 


6.92 


1444 


47.3 


62 


-04- 7 


265.1 


I171.8 


905.7 


425 


6.82 


1465 


48.3 


63 


-95.7 


266.2 


I172.I 


905.9 


419 


6.72 


1488 


49-3 


64 


296.8 


267.2 


T172.4 


905.2 


413 


6.62 


151I 


50.3 


65 


297.8 


268.3 


II72.8 


904.5 


407 


6.53 


1533 


51.3 


66 


29S.8 


269.3 


1173-1 


903.7 


401 


6-43 


.1555 


52.3 


67 


299.8 


270.4 


1173.4 


903.0 


395 


6.34 


1577 


53 3 


68 


300.8 


271.4 


II73-7 


902.3 


390 


6.2=; 


1599 


54.3 


69 


301.8 


272.4 


1174.0 


901.6 


384 


6.17 


162I 


55.3 


70 


302.7 


273.4 


1174.3 


900.9 


379 


6.09 


1643 


56.3 


71 


303.7 


274.4 


1174.6 


900.2 


374 


6.01 


1665 


57.3 


72 


304.6 


275.3 


3174-8 


899.5 


369 


5.93 


1687 


58.3 


73 


305.6 


276.3 


1175.1 


898.9 


365 


5.85 


170^ 


59.3 


74 


306.5 


277.2 


1175-4 


898.2 


360 


5.78 


173I 


60.3 


75 


307.4 


278.2 


1175.7 


897.5 


356 


5.71 


1753 


61.3 


76 


308.3 


279.1 


1176.0 


896.9 


351 


5.63 


1775 


62.3 


77 


309.2 


2S0.0 


1176.2 


896.2 


347 


5.57 


1797 


^3-3 


78 


3 10. 1 


2S0.9 


1176.5 


895.6 


343 


5.50 


i8ig 


^4.3 


79 


310.9 


281.8 


1176.8 


895.0 


339 


5.43 


1840 


^5.3 


80 


3TI.8 


2S2.7 


1177.0 


S94.3 


334 


5.37 


1862 


66.3 


81 


312.7 


283.6 


1177.3 


893.7 


331 


5-31 


1884 


67.3 


82 


313.5 


2S4.5 


1177.6 


893.1 


227 


5-25 


190^ 


68.3 


83 


314.4 


285.3 


1177.S 


892.5 


323 


5.18 


1928 


^^9-3 


84 


315.2 


286.2 


1178.1 


891.9 


320 


5-13 


1950 


70.3 


85 


316.0 


287.0 


1178.3 


891.3 


316 


5.07 


1971 


71.3 


86 


316.8 


287.9 


1178.6 


890.7 


313 


5.02 


1993 


72.3 


87 


317.7 


288.7 


1178.8 


890.1 


309 


4-9^ 


2015 


73.3 


88 


318.5 


289.5 


1179.1 


889.5 


306 


4.91 


2036 


74.3 


89 


319-3 


290.4 


II79-3 


888.9 


303 


4.86 


2058 


75.3 


90 


320.0 


291.2 


1179.6 


888.4 


299 


4.81 


2080 



STEAM, HEAT, COMBUSTION, AND FUELS 

Table i — Continued 



11 





? 




Total 


Heat 






s 









S 4> 


above 32° F. 


rt to 


a 

3 


.si 


^A 






5 ^ 


1 - 


4) ■*-' 


'0 

> 




JO - 
3 S 


bfi . 

3 en 
rt-Q 


5^ 

'0 wi 

cn-Q 


Q 


-a rt 


-a! 


;3 ffi 




15? 




O-l 


5^ 










p^ 


^h^ 


*i 


76.3 


91 


320.8 


292.0 


1179.8 


887.8 


296 


4-76 


.2102 


77.3 


92 


321.6 


292.8 


1 180.0 


887.2 


293 


4.71 


.2123 


78.3 


93 


322.4 


293.6 


1180.3 


886.7 


290 


4.66 


.2145 


79.3 


94 


323.1 


294.4 


1 180. 5 


886.1 


287 


4.62 


.2166 


80.3 


95 


323.9 


295.1 


1180.7 


885.6 


285 


4.57 


.2188 


81.3 


96 


324.6 


295.9 


1181.0 


885.0 


282 


4.53 


.2210 


82.3 


97 


325.4 


296.7 


1181.2 


884.5 


279 


4.48 


.2231 


83.3 


98 


326. T 


297.4 


1181.4 


884.0 


276 


4.44 


.2253 


84.3 


99 


326.8 


298.2 


Ii8i.6 


883.4 


274 


4.40 


.2274 


85.3 


100 


327.6 


298.9 


1181.8 


882.9 


271 


4-36 


.2296 


86.3 


lOI 


328.3 


299.7 


1182.1 


882.4 


268 


4.32 


.2317 


87.3 


102 


329.0 


300.4 


1182.3 


881.9 


266 


4.28 


.2339 


88.3 


103 


329.7 


301. 1 


1182.5 


881.4 


264 


4.24 


.2360 


89.3 


104 


330.4 


301.9 


1182.7 


880.8 


261 


4.20 


.2382 


90.3 


105 


331. 1 


302.6 


1182.9 


880.3 


259 


4.16 


.2403 


91.3 


106 


331.8 


303.3 


1183.1 


879.8 


257 


4.12 


.2425 


92.3 


107 


332.5 


304.0 


1183.4 


879.3 


254 


4-09 


.2446 


93.3 


108 


333.2 


304.7 


1183.6 


878.8 


252 


4.05 


.2467 


94.3 


109 


333.9 


305.4 


1183.8 


878.3 


250 


4.02 


.2489 


95.3 


no 


334.5 


306.1 


1184.0 


877.9 


248 


3.98 


.2510 


96.3 


III 


335.2 


306.8 


1184.2 


877.4 


246 


3.95 


.2531 


97.3 


112 


335.9 


307.5 


1184.4 


876,9 


244 


3.92 


.2553 


98.3 


113 


33^.5 


30S.2 


1184.6 


876.4 


242 


3.88 


.2574 


99.3 


114 


337.2 


308.8 


1184.8 


875.9 


240 


3-85 


.2596 


100.3 


115 


337.8 


309.. 


1185.0 


875.5 


238 


3.82 


.2617 


IOI.3 


116 


338.5 


310.2 


1185.2 


875.0 


236 


3-79 


.2638 


102.3 


117 


339-1 


310.8 


1185.4 


874.5 


234 


3.76 


.2660 


103.3 


118 


339.7 


311. 5 


1185.6 


874.1 


232 


3.73 


.2681 


104.3 


119 


340.4 


312.1 


1185.8 


873.6 


230 


3.70 


.2703 


105.3 


120 


341.0 


312.8 


1185.9 


873.2 


228 


367 


.2764 


106.3 


121 


341.6 


313.4 


1 186. 1 


872.7 


227 


3.64 


.2745 


107.3 


122 


342.2 


314.1 


1186.3 


872.3 


225 


3.62 


.2766 


108.3 


123 


342.9 


314.7 


1186.5 


871.8 


223 


3.59 


.2788 


109.3 


124 


343-5 


315.3 


1186.7 


871.4 


221 


3.56 


.2809 


1 10. 3 


125 


344.1 


316.0 


1186.9 


870.9 


220 


3.53 


.2830 


111.3 


126 


344.7 


316.6 


1187.1 


870.5 


218 


3-51 


2851 


112.3 


127 


345.3 


317.2 


1187.3 


870.0 


216 


3.48 


.2872 


I13.3 


128 


345.9 


317.8 


1187.4 


86Q.b 


215 


3.46 


.2894 



12 



QUESTIONS AND ANSWERS 



Table i — Continued 





£ . 




Total Heat 




<u 


S 


I 


Si— 1 


CO*—) 




Above 


32«F. 


_^ 


S 


bI 


^i 


m , 












3 

> 


to 




13^ 

Oh ^ 




1 - 




^ a; 


<U 1> 


Vh 


03 .ti 


OJ — 


C^ ^ 







CJ rt 


be . 


^^. 




^ J 


th^l 


H3— re 


.^ 


J^ 


«^ 


p tfi 


'0 ^ 


Q 






1 n: 


5 




.^C/5 








ft 




1-3 


0^ 


^3 


. 


IT4.3 


129 


346.5 


318.4 


II87.6 


869.2 


213 


3-43 


.2915 


115. 3 


130 


347.1 


319.1 


II87.8 


868.7 


212 


3.41 


.2936 


116. 3 


131 


347.6 


319.7 


II88.0 


868.3 


210 


3.38 


.2957 


117.3 


132 


348.2 


320.3 


1188.2 


867.9 


209 


3.36 


.2978 


118.3 


133 


348.8 


320.8 


IIS8.3 


867.5 


207 


3.33 


.3000 


119.3 


134 


349.4 


321.5 


II88.5 


867.0 


206 


3.31 


.3021 


120.3 


135 


350.0 


322.1 


II88.7 


866.6 


204 


3.29 


.3042 


121. 3 


136 


350.5 


322.6 


II88.9 


866.2 


203 


3.27 


.3063 


122.3 


137 


351. 1 


323.2 


II89.0 


865.8 


201 


. 3.24 


.3084 


123.3 


138 


351.8 


323.8 


II89.2 


865.4 


200 


3.22 


.3105 


124.3 


139 


352.2 


324.4 


II89.4 


865.0 


199 


3.20 


.3126 


125.3 


140 


352.8 


325.0 


II89.5 


864.6 


197 


3.18 


.3147 


I26c3 


141 


353.3 


325.5 


II89.7 


864.2 


196 


3.16 


.3169 


127.3 


142 


353.9 


326.1 


II89.9 


863.8 


195 


3.14 


.3190 


128.3 


143 


354.4 


326.7 


II90.0 


863.4 


IQ3 


3. II 


.3211 


129.3 


144 


355.0 


327.2 


II90.2 


863.0 


192 


3-09 


.3232 


130.3 


145 


355.5 


327.8 


II90.4 


862.6 


191 


3.07 


.3253 


131.3 


146 


356.0 


328.4 


II90.5 


862.2 


190 


3.05 


.3274 


133.3 


148 


357.1 


329.5 


1 190. 9 


861.4 


187 


3.02 


.3316 


135.3 


150 


358.2 


330.6 


1191.2 


860.6 


185 


2.98 


.3358 


X40.3 


155 


360.7 


333.2 


1192.0 


858.7 


179 


2.89 


.3463 


145.3 


160 


363.3 


335.9 


1192.7 


856.9 


174 


2.S0 


.3567 


150.3 


165 


365.7 


338.4 


1193.5 


855.1 


169 


2.72 


.3671 


155.3 


170 


368.2 


340.9 


1194.2 


853.3 


164 


2.65 


.3775 


160.3 


175 


370.5 


343.4 


1194.9 


851.6 


160 


2.58 


.3879 


165.3 


180 


372.8 


345.8 


1195.7 


849.9 


156 


2.51 


.3983 


170.3 


185 


375.1 


348.1 


1196.3 


848.2 


152 


2.45 


.4087 


175.3 


190 


377.3 


350.4 


1197.0 


846.6 


148 


2.39 


.4191 


180.3 


195 


379.5 


352.7 


1197.7 


845.0 


144 


2.33 


.4296 


185.3 


200 


381.6 


354.9 


1198.3 


843.4 


141 


2.27 


.4400 


190.3 


205 


383.7 


357.1 


1 199.0 


841.9 


138 


2.22 


.4503 


195.3 


210 


385.7 


359.2 


1199.6 


840.4 


135 


2.17 


.4605 


200.3 


215 


387.7 


361.3 


1200.2 


838.9 


132 


2.12 


.4707 


205.3 


220 


389.7 


362.2 


1200.8 


838.6 


129 


2.06 


.4^b2 


245.3 


260 


404.4 


377-4 


1205.3 


827.9 


no 


1.76 


.5686 


28S.3 


300 


417.4 


390.9 


i2og.2 


818.3 


96 


1.53 


.6515 


485.3 


500 


467.4 


443.5 


1224.5 


781.0 


59 


.94 


1.062 


685.3 


700 


504.1 


482.4 


1235.7 


753.3 


42 


.68 


1.470 


985.3 


1000 


546.8 


528.3 


1248.7 


720.3 


30 


.48 


2.082 



STEAM, HEAT, COMBUSTION, AND FUELS 13 

Ques. 8. — How much pressure does the atmosphere 
exert upon the surface of the earth? 

Ans. — 14.7 pounds upon each square inch of the 

earth's surface. 

Ques. 9. — What is understood by gauge pressure? 

Ans. — Gauge pressure is the pressure over and above 
the 14.7 pounds atmospheric pressure. 

Ques. 10. — What is absolute pressure? 

Ans. — Absolute pressure is the total pressure above a 
perfect vacuum. It equals the sum of the gauge pressure 
and the atmospheric pressure. 

Ques. 11. — How does pressure influence the boiling 
point of water? 

Ans. — The higher the pressure, the higher must the 
temperature of the water be raised in order to cause it to 
boil. 

Ques. 12.~In what way does pressure affect the vol- 
ume of steam? 

Ans. — The higher the pressure, the smaller will be the 
volume of the steam generated from a given weight of 
water. 

Ques. 13. — In what light should steam be considered 
relative to work? 

Ans. — As an agent through which heat performs the 
work. 

Ques. 14. — What is the most important property of 
steam.'* 

Ans. — Its expansive force. 

Ques. 15. — What law governs this expansion? 

Ans.— Boyle's law of expanding gases. 



14 QUESTIONS AND ANSWERS 

Ques. 16. — Define Boyle's law. 

Ans. — The volume of all elastic gases is inversely pro- 
portional to their pressure. 

Ques. 17.— What is heat? 

Ans. — Heat is a form of energy which may be applied 
to or taken away from bodies. 

Ques. 18. — Name the original source of heat, at least 
for this planet. 

Ans. — The sun. 

Ques. 19. — How was this heat made available for 
man's use? 

Ans. — By being stored up in oil, wood, and the coal 
formations millions of years ago, by the rays of the suno 

Ques. 20. — What is the relation of heat to matter? 

Ans. — All matter is charged with heat in a greater or 
less degree, depending upon the nature of the matter. 

Ques. 21. — What is the specific heat of any substance? 

Ans. — The ratio of the quantity of heat required to 
raise a given weight of that substance 1 degree in temper- 
ature, to the quantity of heat required to raise the same 
weight of water 1 degree in temperature, the water being 
at its maximum density, 39.1 degrees. 

The following table gives the specific heat of different 
substances in which engineers are most generally inter- 
ested: 

Table No. 2 

Water at 39.1 degrees Fahrenheit i.OOO 

Ice at 32 degrees Fahrenheit 504 

Steam at 212 degrees Fahrenheit o 480 

Mercury 033 

Cast iron 130 



STEAM, HEAT, COMBUSTION, AND FUELS 15 

Table No. 2 — Continued 

Wrought iron 113 

Soft steel 116 

Copper 095 

Lead 031 

Coal « 240 

Air 238 

Hydrogen 3.404 

Oxygen 218 

Nitrogen 244 

Ques. 22. — What is sensible heat? 

Ans. — Heat imparted to a body, and warming it. 
Sensible heat in any substance can be measured in degrees 
of a thermometer. 

Ques. 23.— What is latent heat? 

Ans. — Heat given to a body and not warming it; that 
IS, the heat that is not shown by the thermometer. 

Ques. 24. — Is the heat lost that thus becomes latent? 

Ans. — It is not. On the contrary, it was required to 
produce the change in the body from the solid to liquid, 
or from the liquid to the gaseous state. For instance, in 
the transformation of ice into water, 180 degrees of heat 
becomes latent, and in changing the water into steam at 
atmospheric pressure 965.7 degrees of heat become 
latent. * 

Ques. 25. — What is the first law of thermo-dyna- 
mics? 

Ans. — Heat and work are mutually convertible; that 
is, a certain amount of work will produce a certain 
amount of heat, and the heat thus produced will, by its 
disapoearance, if rightly applied, produce a fixed amount 
ax mecManical energy. 



16 QUESTIONS AND ANSWERS 

Ques. 26. — How is heat measured with relation to 
work? 

Ans. — -By the thermal unit. 

Ques. 27. — What is a thermal unit? 

Ans. — It is the quantity of heat required to raise the 
temperature of one pound of pure water one degree, or 
from 39 degrees, its temperature of greatest density, to 
40 degrees. 

Ques. 28. — What is the mechanical equivalent of 
heat? 

Ans. — The mechanical equivalent of heat is the 
energy required to raise a weight of 778 pounds one foot 
high, or a weight of one pound 778 feet high; in other 
words, 778 foot pounds. This amount of energy is stored 
in one thermal unit, or heat unit. 

Ques. 29. — In how many ways is heat transmitted? 

Ans. — In two ways: — First by conduction; second, by 
radiation. 

Ques. 30. — What is conduction of heat? 

Ans. — Conduction is the transmission of heat from 
one body to another in direct contact with it. 

Ques. 31. — Are all bodies equally good conductors of 
heat? 

Ans. — No. The best conductors of heat are the 
metals, silver, copper, tin, steel, lead. The poorest 
conductors, or nonconductors, as they are termed, are 
hair, wool, straw, wood, liquids, and **dead''' air, that is, 
air not in circulation. 

Ques. 32. — What is radiation of heat? 

Ans. — Radiation is the transmission of heat from one 



STEAM, HEAT, COMBUSTION, AND FUELS 17 

body to another through an intervening space between 
the bodies. 

Ques. 33. — How is the heat in the furnace or fire-box 
of a boiler transmitted to the water in the boiler? 

Ans. — By radiation and conduction through the heat- 
ing surface of the boiler. 

Ques. 34. — What is combustion? 

Ans. — Combustion is the chemical union of the carbon 
and hydrogen of the fuel with the oxygen of the air. 

Ques. 35. — What is one of the main factors in the 
proper combustion of fuels, especially coal? 

Ans.— A proper supply of air. 

Qu^s. 36. — What is the principal constituent of coal, 
oil, and most other fuels? 

Ans» — Free or fixed carbon. 

Ques. 37. — Are there other combustibles in fuels? 

AnSe — Yes; hydrocarbons, a chemical combination of 
carbon and hydrogen in different ratios. 

Ques. 38.— State tlie composition of air. 

Ans. — By volume, 21 parts oxygen and 79 parts 
nitrogen; by weight, 23 parts oxygen and 77 parts 
nitrogen. 

Ques. 39. — In what proportion do the atoms of carbon 
and hydrocarbons combine with the atoms of oxygen to 
form perfect combustion? 

Ans. — One atom of carbon combines with two atoms 
of oxygen, expressed by the chemical symbol CO^. 

Ques. 40. — In the process of combustion, which com- 
bustible burns first? 

Ans, — When fresh fuel is added to the fire, the hydro- 



18 QUESTIONS AND ANSWERS 

carbons distill in the form of gas, and if the conditions 
of draught, admission of air, etc., are right, this gas will 
ignite and burn during its passage through the furnace 
and combustion chamber; otherwise it passes out of the 
stack in the form of smoke. 

Ques. 41. — What are the common products of com- 
bustion? 

Ans. — First, carbonic acid, resultant from the 
chemical union of one atom of carbon with two atoms of 
oxygen (symbol CO^); second, water vapor, resultant 
from the chemical union of two portions of hydrogen, and 
one portion of oxygen (symbol H^O); third, inert gases, 
like nitrogen, also unassociated oxygen, ash, and other 
products, due to the impurities contained in the coal, or 
other fuel. 

Ques. 42.- — In what form does the fixed carbon appear 
during the process of combustion? 

Ans. — After the hydrocarbons have left it, the fixed 
carbon appears in the form of a glowing mass of coke, 
uniting with the oxygen to form carbonic acid, and all 
the heat stored in the carbon is liberated, provided the 
supply of air is correct; otherwise carbon monoxide 
(symbol CO) is formed, and only about one-third of the 
stored heat is liberated, the larger portion of the carbon 
passing off in the form of soot and smoke. 

Ques. 43. — How many thermal units are contained in 
one pound of carbon? 

Ans. — 14,500 thermal units. 

Ques. 44. — Theoretically, how much air is required 
V)r the complete combustion of one pound of coal? 



STEAM, HEAT, COMBUSTION, AND FUELS 19 

Ans. — By weight, 12 pounds; by volume, 150 cubic feet, 

Ques. 45. — Is this law carried out in practice? 

Ans. — It is not; a much larger quantity of air (20 to 
24 pounds per pound of coal) being supplied in order to 
insure that all the atoms of carbon may find oxygen. 

Ques. 46. — In what two ways is the air supplied to 
boiler furnaces? 

Ans. — First, by natural draught; second, by artificial 
or forced draught. 

Ques. 47. — What causes natural draught? 

Ans. — The air in the furnace and uptake becomes 
heated and c6nsequently much lighter in weight than art 
equal column of outside air. The heated air is therefore 
continually rising and passing out of the funnel or smoke- 
stack, while the outside air rushes into the ash-pit and: 
up through the grates to replace it. 

Ques. 48. — How many systems of artificial or forcecf 
draught are there? 

Ans. — There are two principal systems: First, that 
in which the air is forced directly into the ash-pits, 
through conduits leading directly from the fan, or other 
source of the blast; second, that in which the air is forced 
directly into the fire-room or stoke-hole, which is made 
air-tight for this purpose, and from thence the air finds 
its way into the furnaces on the same principle as when 
natural draught is employed. 

Ques. 49. — Mention the two most important factors 
in the regulation of combustion. 

Ans. — First, the draught; second, the kind and 
quality of the fuel. 



20 QUESTIONS AND ANSWERS 

Ques. 50. — What is meant by the expression "rate of 

combustion?'' 

Ans. — The rate of combustion means the number of 
pounds of fuel burned per square foot of grate surface 
per hour. 

Ques. 51. — What are the usual rates of combustion 
with natural draught? 

Ans. — For stationary boilers with shaking grates, 
from 12 to 18 pounds of coal per hour; for marine 
boilers, from 15 to 25 pounds. 

Ques. 52. — What are the rates of combustion with 
artificial or forced draught? 

Ans. — For stationary boilers, 25 to 35 pounds; for 
marine boilers, 20 to 50 pounds. 

Ques. 53. — How should the air-supply be regulated in 
order to bring about complete combustion? 

Ans. — Complete combustion can be secured only when 
the air is brought into direct contact, not only with the 
fuel, but also with the gases as they develop. If the air 
passing into the furnace above the fuel is first heated, 
much better results can be attained. 

Ques. 54. — Why is it desirable to admit air (heated if 
possible) above the fire? 

Ans. — In order to supply to the hydrocarbons the 
oxygen necessary to their complete combustion. 

Ques. 55. — What will be the result if the supply of 
oxygen above the fire is not sufficient? 

Ans. — A portion of the hydrocarbons will pass off 
unburned, and of other portions, only the hydrogen is 
burned, leaving the carbon to pass off as soot or smoke. 



STEAM, HEAT, COMBUSTION, AND FUELS 21 

Ques. 56. — State another reason why the air should be 
admitted above the fire. 

Ans. — If carbon monoxide (CO) has been formed in 
the combustion of the fixed carbon, the air above the fir^ 
would burn this into carbonic acid, thereby liberating t 
large additional amount of heat. 

Ques. 57. — What is indicated by the formation ol 
much smoke and soot? 

Ans. — Incomplete combustion, as smoke and soot are 
simply unoxydized particles of carbon. 

Ques. 58. — Is a high furnace temperature conducive 
to good combustion? 

Ans. — It is; because the hydrocarbons unite with the 
oxygen much more quickly, and the fixed carbon also is 
much more completely united with oxygen in a high 
temperature. 

Ques. 59. — Mention a very efficient agency for main- 
taining a high furnace temperature. 

Ans. — Fire-brick arches and bafflers, for the gases to 
impinge against. 

Ques. 60. — Assuming that good combustion is taking 
place in the boiler furnace, what will be the furnace tem- 
perature? 

Ans. — From 2,500 to 3,000 degrees Fahrenheit. 

Ques. 61. — What are the fuels most commonly used 
in boiler furnaces? 

Ans. — Coal, wood, and oil. 

Ques. 62. — What per c ent of volatile matter is con- 
tained in most of the coals used in the marine service? 

Ans. — About 20 per cent. 



•23 QUESTIONS AND ANSWERS 

Ques. 63. — What are the advantages of fuel oil? 
Ans. — Greater evaporative power for same weight and 
bulk, ease of manipulation, perfect control of the com- 
bustion to suit requirements of service, and cleanliness. 

Ques. 64. — What are the principal objections to the 
use of oil as fuel for boilers? 

Ans. — First, certain dangers involved in storing and 
■using it; second, limited supply. 

Ques. 65. — State the difference between the heating 

value of a pound of bituminous coal and a pound of wood. 

Ans. — One pound of coal will evaporate from 8 to 

9 pounds of water; one pound of wood will evaporate 

from 2^ to 3/^ pounds of water. 

Ques. 66, — What are the two principal kinds of coal 
i:sed as fuel for boilers? 

Ans. — First, anthracite or hard coal; second, bitumin- 
ous or soft coal. 

Ques. 67. — State the composition of hard coal. 

Ans. — ^Carbon per cent 91.05 

Volatile matter ** 3.45 

Moisture " 1.34 

Ash •' 4.16 

100.00 
[ Ques. 68. — State the composition of the best soft coals. 

Ans. — t Fixed carbon per cent 75.02 

Volatile matter ** 20.34 

Moisture ** .61 

Ash '• 3.47 

Sulphur ** .56 

100.00 

"Thurston. tKent. 



STEAM, HEAT, COMBUSTION, AND FUELS 



23 



Ques. 69. — Does this analysis apply to all bituminous 
coals? 

Ans.— No; some of the poorer kinds run as low as 40 
per cent in carbon, 32 per cent in hydrocarbons, and 12 
per cent in ash. 

Ques. 70. — How do these impurities aflfect the value 
of coal as a fuel? 

Ans. — The mineral combination of sulphur and iron 
affects the keeping qualities of some coals. Ashes and 
mineral substances form clinkers on the grate bars by 
fusing together, thereby greatly impeding the passage of 
air through the fire. 

Table No. 3 
Analysis of Coal from Different States. 



State 


Kind of Coal 


Moist- 
ure 


Vola- 
tile 
Matter 


Fixed 
Carbon 


Ash 


Sul- 
phur 


Pennsylvania 


Youghiogheny 


1. 03 


36.49 


59.05 


2.61 


0.81 


«( 


Connellsville 


1.26 


30.10 


59.61 


8.23 


0.73 


West Virginia 


Quinimont 


0.76 


18.65 


79.26 


I. II 


0.23 


* ' 


Fire Creek 


0.61 


22.34 


75.02 


1.47 


0.56 


E. Kentucky 


Peach Orchard 


4.60 


35.70 


53.28 


6.42 


1.08 


** 


Pike County 


i.£o 


26.80 


67.60 


3.80 


0.97 


Alabama 


Cahaba 


I.Cj 


33.28 


63.04 


2.02 


0.53 


(( 


Pratt Co.'s 


1.47 


32.29 


59.50 


6.73 


1.22 


Ohio 


Hocking Valle3' 


6.59 


35.77 


49.64 


8.00 


1.59 


<( 


Muskingum ** 


3.47 


37.^3 


53.30 


5.35 


2.24 


Indiana 


Block 


8.50 


31.00 


57.50 


3.00 




t < 


** 


2.50 


44.75 


51.25 


1.50 




W. Kentucky 


Nolin River 


4.70 


33' ^A- 


54.Q4 


11.70 


2.54 


4 < 


Ohio County 


3.70 


30.70 


45.00 


3.16 


1.24 


lUinois 


Big Muddy 


6.40 


30.60 


54.60 


8.30 


1.50 


ti 


Wilmington 


15.50 


32.80 


39.90 


11.80 




•t 


*' screenings 


14.00 


28.00 


34.20 


23.80 




•f 


Duquoin 


8.90 


23.50 


60.60 


7.00 





Ques. 71. — How is coal measured? 

Ans. — Usually ^ - weight in pounds or tons. For 
storage purposes between 42 and 44 cubic feet per ton of 
3,240 pounds are aiiowed. 



24 QUESTIONS AND ANSWERS 

Ques. 72. — What is the heating value in thermal units 
of one pound of bituminous coal? 

Ans. — 12,000 to 14,500 thermal units, depending upon 
the quality of the coal. 

Ques. 73. — What is the average composition of wood? 

Ans. — About 50 per cent of carbon, 40 per cent of 
oxygen, some hydrogen, and about 1 per cent of ash. 

Ques. 74. — What is the average heating value of 
wood expressed in thermal units? 

Ans. — From 6,000 to 8,000 thermal units per pound. 

Ques. 75. — What woods are generally used for fuel? 

Ans. — Hickory, oak, beech, pines, and firs. 

Ques. 76. — What are the principal disadvantages in 
the use of wood as a fuel for steam boilers? 

Ans. — First, a limited supply; second, great bulk in 
comparison to its heating value. 

Ques. 77. — State the composition of fuel oil. 

Ans. — Fuel oil contains about 86 per cent of carbon, 
13 per cent of hydrogen, and 1 per cent of oxygen. 

Ques. 78. — What is the heating value of fuel oil? 

Ans.— 20,000 to 22,000 thermal units per pound of oil. 

Ques. 79. — What are the relative heating values of 
coal and wood? 

Ans. — One pound of coal is equal to 2/4 pounds of 
wood. 

Ques. 80. — What is the best all-around fuel, with high 
heating value, and at reasonable cost? 

Ans. — Coal. It is easily obtainable very nearly every- 
where; it is safe to handle, and has small bulk in propor- 
tion to its heating: value. 



CHAPTER II 

THE BOILER. 

Ques. 81. — What are the leading types of boilers in 
use at the present day in the stationary and marine 
service? 

Ans. — First, fire-tube boilers; second, water-tube 
boilers. 

Ques. 82. — In what respect do they diiifer? 

Ans. — Fire-tube boilers have the hot gases inside the 
tubes and the water surrounding them, while in water- 
tube boilers the water is inside the tubes and the hot gases 
and flame are on the outside. 

Ques. 83. — Are boilers classified in any other way? 

Ans. — Yes ; low-pressure boilers, in which 55 to 60 
pounds is the limit, and high-pressuie boilers, carrying 
from 150 to 300 pounds pressure. 

Ques. 84. — What are the most common forms of fire- 
tube boilers? 

Ans. — First, the horizontal tubular boiler; second, 
the vertical tubular boiler; third, the Scotch boiler; 
fourth, the flue and return tube boiler; fifth, the Western 
river boiler. 

Ques. 85. — Describe the horizontal tubular boiler. 

Ans. — It consists of a cylindrical shell, having tubes 
of from 2 to 4 inches in diameter extending from head 
to head. There is usually a dome on top, and the 
boiler is set in brickwork, having the furnace underneath. 
The heated gases pass first under the boiler, and then 

25 



26 QUESTIONS AND ANSWERS 

return through the tubes to the breeching or uptake 

leading to the stack. 

Ques. 86. — What are the leading features of the verti- 
cal tubular boiler? 

Ans. — A cylindrical shell, having the fire-box or fur- 
nace in its lower end. The bottom ends of the tubes are 
expanded into the tube-sheet of the fire-box, and the top 
ends of the tubes are expanded into the top head of the 
boiler, and conduct the gases directly to the stack. 

Ques. 87. — Are the tubes entirely submerged in this 
class of boilers? 

Ans. — Not in all cases. Some forms of vertical boilers 
have a submerging chamber above the upper tube-sheet. 
This allows of a steam space above the top ends of the 
tubes, surrounding the smoke uptake, or smoke flue lead- 
ing to the stack. The tubes are thus entirely submerged. 
In the flush-tube boiler the steam and water space is below 
the upper tube-sheet or head of the boiler, thus leaving 
the upper portion of the tubes surrounded only by steam. 

Ques. 88. — Describe the Scotch boiler. 

Ans. — The Scotch boiler may be made either single- 
ended or double-ended. The shell is cylindrical, with 
flat heads. The diameters range from 10 to 15 feet, and 
in some cases even 20 feet, with a length of from 7 to 11 
feet. The Scotch boiler is horizontal, and is provided 
with two or more large corrugated furnace flues, placed 
near the bottom of the boiler, and extending from the 
front head to the combustion chamber in the rear. 

Ques. 89 — What is the diameter of these corrugated 
flues? 



THE BOILER 



27 



Ans.— From ^A to 4>4 feet, depen ng upon the size 
of the boiler. 

Ques. 90. — How ar^ these furnace flues secured in 
:he boiler? 




Ans. — One end of the flue is riveted into the front 
head of the boiler, and the back end of the flue is rivetr A 
into the front sheet of the combustion chamber. 



28 



QUESTIONS AND ANSWERS 



Ques. 91.— Describe the combustion chamber of the 
Scotch boiler. 

Ans. — It is a chamber built of steel boiler plate, 
located at the rear end of the boiler, and entirely sur- 
rounded by water. A nest of tubes extends from the' 
front sheet of the combustion chamber, above the cor- 
rugated furnace flue, to the front head of the shell. 




Fig. 2. Standard Horizontal Boiler with Full-arch Front Setting. 



Ques. 92. — Describe the course of the heated gases in 
the Scotch boiler. 

Ans. — The furnaces proper, are placed within the cor- 
rugated flues, near the front end. The gases and smoke 
pass through the flues to the combustion chamber, and 
from thence return through the small tubes to the smoke- 
box in front, and from there out through the stack. 

Ques. 93. — How are the flat sides of the combustion 
chamber stayed? 



THE BOILER 



n 




Fig. 3. Vertical Tubular Boiler, with Full-I^Ength Tubes. 



5U QUESTIONS AND ANSWERS 

Ans. — By stay-bolts connecting with the shell and the 
back head. The small tubes serve as stays for the front 
sheet. 




Fig. 4. Vertical Marine Boileb, Showing Details 

OF Bracing. 



Ques. 9-i. — Wl:at is meant by double-ended Scotch 
boilers? 

Ans. — Boilers having furnaces at each end. A double- 
ended Scotch boiler is in fact two single-ended boilers i 
placed back to back. I 



nil 



liOILICR 



31 



Ques. 95. — What advantage has the Scotch boiler 
over other types? 

Ans. — A very large amount of heating surface in 
proportion to its cubic contents. 

Ques. 96. — What are the disadvantages connected 
with the use of the Scotch boiler? 










0000000000 
0000000000 



000000 0000000000 




Fig. 5. Singi,e-Knded Scotch Marine Boiler. 



Ans. — First, defective water circulation; second, 
liability to leaky tubes; third, unequal expansion of the- 
parts, thereby setting up severe strains. 

Ques. 97. — Is the Scotch boiler much used? 

^ns. — It is in almost universal use in the large ocean- 
going mercnanr vessels. 



32 



QUESTIONS AND ANSWERS 



Ques. 98. — What are the distinctive features of the 
flue and return-tube boiler? 

Ans. — This form of boiler is cylindrical in shape in 
that part of the shell containing the large flues and 
small return tubes, but resembles a locomotive boiler in 
that portion containing the fire-box. 




Fig. 6. Doubi:,e-Knded Scotch Marine Boiler, Sectional View. 

Ques. 99. — Describe the action of the heat in this 
boiler. 

Ans. — The furnace or fire-box, resembling that of a 
locomotive, is located in the front end of the boiler. 
From thence large flues conduct the heated gases to the 
combustion chamber in the rear, similar to that of a 
Scotch boiler, and from there the gases return through 
the small tubes to the uptake. 



THE BOILER 



33 




34 



QUESTIONS AND ANSWERS 



Ques. 100. — Describe the Western river boiler. 

Ans. — This boiler is usually very long (25 to 30 feet) 
^n proportion to its diameter. It consists of a cylindrical 
shell having two or more flues of large diameter (12 to 
14 inches) extending its entire length. It is set in brick- 
work in the same manner as the horizontal tubular boiler 
i-:. '-^e gases passing underneath the shell to the rear, and 
thence returning through the large flues to the uptake 




Fig. 8. The Bonus-Freeman Water-Tube Boiler. 

leac '.r.g to the stack. It is a very simple boiler, and will 
"'v.-'.thstand high pressures and hard usage. 

Ques. 101. — Describe the locomotive boiler. 

Ans. — The locomotive boiler consists essentially of a 
rectangular fire-box and a cylindrical shell. A large 
number cf tubes of small diameter (2 inches) oass 
through the shell from the fire-box to the smoke-box, a 
^continuation of the barrel at the front end. 



THK nOILER 



35 




36 



QUESTIONS AND ANSWERS 



Ques. 102. — How is the fire-box joined to the outer 
shell at the bottom? 

Ans. — By a forged ring called the mud-ring, made of 
wrought iron or steel, through which long rivets pass, 
uniting the fire-box sheet and the outer sheet. 

Ques. 103. — How are the flat sides of the fire-box 
stayed? 

Ans. — By stay-blots screwed through the outer shell, 
into and through the fire sheet, and having both ends 
riveted down cold. 

Ques. 104. — How is the flat crown-sheet of a locomo- 
tive boiler stayed? 







Fig. 10. CoRNi5H Boiler. 



Ans. — By a system of crown-bars, made in the shape 
of double girders, the ends of which rest upon the side 
sheets of the fire-box. Crown-bolts pass up through the 
crown-sheet and crown-bars, and are secured by nuts 
resting upon saddles on top of the crown-bars. The 
heads of the bolts support the crown-sheet. 

Ques. 105. — Is the locomotive boiler an economical 
boiler for stationary purposes? 

Ans. — It is not. 

Ques. 106. — Are there any other forms of cylindrical 
shell boilers besides those already referred to? 

Ans. — Yes; the Cornish boiler, having a large central 



THE BOILER 



37 



flue, in one end of which the furnace is located; the Lan- 
cashire boiler, a modification of the Cornish, containing two 
internal furnace flues, and the Continental boiler. 

Ques. 107. — What is meant by Galloway tubes as 
applied to a boiler? 

Ans. — Galloway tubes are conical-shaped water tubes 
which stand in an inclined position in the large flues of 
the Lancashire boiler back of the furnaces, and serve to 
circulate the water from the space below, to the space 
above the flues. They also act as bafflers to the gases in 
their passage through the flues, and thus provide increased 
heating surface. 








^^^^^^^^s^^ 


^^^^^ 


ra 






iJ=^^^=--=^=^.^z-^-= 


^^w^ 




Fig. 11. The IvANCashire Boiler. 



Fig. 12. The Galloway 
Boiler. 



Ques. 108. — Describe the Continental boiler. 

Ans. — The Continental boiler is a modification of the 
Scotch boiler, and is used to a large extent in the marine 
service. It is provided with a Morison corrugated fur- 
nace, and its efficiency as a steam generator has been 
established by a long series of practical tests. 

Ques. 109. — What are the leading characteristics of 
the Bonson boiler? 

Ans. — The Bonson boiler is a combination of the 
tubular and water-tube types. The water-tube member 
is in the form of a flat arch, and serves as a roof to the 
furnace. The cylindrical shell rests uDon and is con- 



38 



QUESTIONS AND ANSWERS 



nected with front and rear steel saddles (water-chambers) 
and the water-tubes are connected with the lower portion 
of these saddles, 

Ques. 110. — What route do the gases take in passing 
from the furnace of the Bonson boiler to the smoke- 
stack? 




Fig. 13. Continental Boiler, with Morison Corrugated 
Furnace, for Marine or Stationary Service. 



Ans. — They pass first under the water-tubes, which 
are lined with a special tile made of fire-clay, the sides of 
the furnace being also lined with fire-brick. The gases, 
after passing into the combustion chamber, at the rear, 
ascend and return through the fire-tubes in the shell, and 
from thence into the uptake at the front. 

Ques. 111. — What are the leading characteristics of ^ 
water-tube boilers? 



THE BOILER 39 

Ans. — In water-tube boilers the larger part of the 
heating surface consists of tubes of moderate size (1 to 4 
inches in diameter). There is always some form of 
separator, drum or reservoir into which the tubes lead. 
In this drum the steam is separated from the water. In 
some forms of water-tube boilers this shell or drum is of 
considerable size. 




Fig. 14. The Bonson Boii^er and Setting. 

Ques. 112. — Is this drum exposed directly or indi- 
rectly to the heat? 

Ans. — It is generally exposed indirectly, as the upper 
part is used for steam space. 

Ques. 113. — What advantage is there in having a 
large size steam and water-drum? 

Ans. — The advantage of having a good free water 
surface for the disengagement of the steam. The water 
occupies about one-third of the lower portion of the drum. 



40 



QUESTIONS AND ANSWERS 



Ques. 114. — Are the upper ends of the tubes in all 
water-tube boilers entirely filled with water? 

Ans. — Not in all cases. In some forms of water-tube 
boilers the upper ends of the tubes extend above the 
water level. 

Ques. 115. — How are these different forms of water- 
tube boilers designated? 

Ans. — First, as drowned tubes; second, as priming 
tubes. 




Fig. 15. Steei* Saddle of Bonson Boii^er. 



Ques. 116. — What are some of the advantages of 
water-tube boilers? 

Ans. — They may be made light, powerful and able to 
withstand high pressures. They are quick steamers, 
that is, steam may be raised rapidly from cold water; 
also, the circulation of the water in them is good gen- 
erally. 

Ques. 117. — What are some of the disadvantages 
attending the use of water-tube boilers? 

Ans. — They are difficult to inspect and clean. Also, 
owing to the large number of joints, leaks are liable to 
occur. 



THE BOILER 41 

Ques. 118. — Describe briefly the Babcock & Wilcox 
water-tube boiler. 

Ans. — There is a large horizontal cylindrical shell at 
the top for the purpose of supplying steam and water- 
space. The lower half of this shell contains water, and 
the upper half steam. The tubes are expanded into 
headers at each end. At the front end these headers are 




Fig. 16. Babcock and Wii,cox Boii^er, for Land Service. 

brought up near the shell, to which they are connected 
by a cross connection. The back end headers are con- 
nected to a mud-drum at the bottom, and to the shell at 
the top by slightly inclined tubes. The back headers 
being lower than the front headers, the tubes are thus 
inclined from front to back. 

Ques. 119. — In what style are the tubes connected to 
the headers? 

Ans. — They are staggered. 



42 



QUESTIONS AND ANSWERS 



Ques. 120. — What is meant by staggered tubes? 
Ans. — Staggered tubes are those which are not placed 
in vertical rows, that is, one directly above the other. 




Fig. 17. Babcock and Wilcox "Alert" Type Marine Boii^Er. 
FromB. & W. "Book Marine Steam," p. 154. 

Ques. 121. — What are the facilities for cleaning these 
tubes? 

Ans. — At each end of each tube there are hand-holes 
provided. 

Ques. 122. — Describe the course of the gases for the 
Babcock & Wilcox boiler. 



THE BOILER 43 

Ans. — A brick bridge wall at the bacK enu ot the fur- 
nace, together with special tiles placed among the tubes, 
compel the gases to first pass up among the tubes until 
they come in contact with the bottom of the shell for 
about two-thirds of its length from the front end. At 
this point a hanging bridge wall and special tiles deflect 
the gases downward in their course, and they again 
circulate among the tubes, passing underneath the tiles 
and up among the tubes again. The products of com- 
bustion thus pass over and around the tubes three times 
on their way to the uptake. 

Ques. 123.— What portions of this boiler constitute 
the heating surface? 

Ans. — The tubes, headers, and the lower half of the 
shell. 

Ques. 124. — What course does the water take in its 
circulation in this boiler? 

Ans. — Down from the shell at the rear to the water- 
tubes, thence forward and upward through the tubes. 
In its course through the tubes it becomes partially vap- 
orized and of less density. It then passes up into the 
shell at the front, where the steam is disengaged. 

Ques. 125. — Is the Babcock & Wilcox boiler much 
used in the marine service? 

Ans. — Yes, it is used extensively in the British and 
United States navies, also in merchant steamers. 

Ques. 126. — Is the form of this boiler the same for 
mairine as for land service? 

Ans. — It is not. The chief features in which it diflfers 
from the land boiler are, first, a very much larger grate 



44 



QUESTIONS AND ANSWERS 



area; second, the cylindrical sl:ell is set transversely to 
the direction of the tubes; third, the fire-doors are located 
at what would be the rear of the land boiler; fourth, the 
tubes are much shorter, owing to the contracted space 
allowed on ocean steamers; fifth, the brickwork is sur- 
rounded outside by a metal casing. 




Fig. 18. The Caldweli, Boiler. 

Ques. 127. — Are there any other forms of water-tube 
boilers patterned after the Babcock & Wilcox boiler? 

Ans. — There are several, prominent among which are 
the Caldwell and the Root boilers. 

Ques. 128. — Describe the Caldwell boiler. 

Ans. — It is similar in construction to the Babcock & 
Wilcox, except that the tubes, instead of being staggered 
vertically, are placed one directly above the other, w^ith 
specially shaped fire-brick laid across alternate spaces 
between the tubes to deflect the gases. 



THE BOILER 



45 



Ques. 129. Describe the Root water-tube boiler. 

Ans. — It consists of a nest of 4-inch tubes expanded 
into headers which are connected at front and back with a 
set of steam and water-drums about 15 inches in diameter. 
The tubes are inclined at an angle of about 20 degrees 
from the horizontal. At the rear end of each overhead 
water and steam-drum is a connection leading to the 




Fig. 19. The Root Water-Tube Boii^er. 

steam-collecting header above, placed transversely to the 
direction of the other drums, and from this header two 
connecting pipes lead to a large steam-drum located at 
about the center of the boiler, and above all. 

Ques. 130. — How does the water circulate in the Root 
boiler? 

Ans. — It descends through vertical connecting pipes 
from the feed-drum at the rear to the mud-drum beneath^ 



46 



QUESTIONS AND ANSWERS 



From thence it passes into the back and lower ends of the 
tubes, and on up through the tubes, and into the over- 
head drums, into the upper halves of which the steam is 
disengaged. 

Ques. 131. — Describe the Cahall water-tube boiler. 

^nc — The Cahall boiler is vertical, having a nest of 




Fig. 20, The Cahali. Vertical Boiler. 



water-tubes standing nearly vertical. These tubes are 
connected with a shallow water-drum at the bottom, and 
a larger and deeper water and steam-drum at the top. 
The furnace is located alongside of the mud-drum, and 
the gases traverse among the tubes in a circuitous manner 
owing to bafflers placed am^ong the tubes. 



THE BOILER 4'J 

Ques. 132. — How do the grases escape to the stack ;o 
this boiler? 




Fig. 21. WiCKEs Verticai, Water-Tube Boiler. 

Ans. — Extending through the center of the annular 
drum at the top is a flue through which the products of 
combustion find their way to the uptake. 



48 



QUESTIONS AND ANSWERS 



Ques. 133. — Of what form is the Wickes boiler? 

Ans. — The Wickes boiler consists of tipper and lower 
vertical drums connected by vertical tubes. The furnace 
is external. 




Fig, 22. Ths Stirling Boiler. 



Ques. 134. — What course do the gases take in their 
passage to the stack, in the Wickes boiler? 

Ans. — A thin partition wall of fire-brick is built 
between two adjoining middle rows of tubes. This waJl 
causes the sases first to ascend to the top, and tl'-.en down- 



THE BOILER 



49 



wards to the chimney flue at the bottom and opposite to 
the furnace. 

Ques. 135. — Describe the Stirling boiler. 

Ans. — In the Stirling water-tube boiler there arc 
three horizontal steam and water-drums at the top, anrf 




I 



Fig. 23. Thornycroft Boiler. 



one water-drum at the bottom. These drums are con- 
nected by three divisions of inclined and curved tubes. 

Ques. 136. — How are the products of combustion led 
from the furnace to the uptake, in the Stirling boiler? 

Ans. — Bafflers of fire-brick are placed back of the two 
first divisions of tubes^ The first baffler causes the gases 



50 



QUESTIONS AND ANSWERS 



to ascend to the top of the first division of tubes; the 
second baffler deflects the gases downwards, around and 
among the tubes of the second division. The draught is 
then upwards again, surrounding the tubes composing 
the third division, thence to the stack. 




Fig. 24. The Nici^ausse Boii^er. 

Ques. 137. — Describe the Thornycroft boiler. 

Ans. — The Thornycroft boiler is adapted for use on 
torpedo boats and high-speed yachts. A large horizontal 
steam-drum at the top is connected to a water-drum at 
the bottom by two groups of curved tubes of small 



THE BOILER 



51 



diameter. The grates are located on each side of the 
water-drum. There are also two smaller drums at the 
bottom, one on each side, connected to the middle drum 
by small pipes. 




Fig. 25. The Niclausse Boii^er— Side View. 



Ques. 138. — How does the water circulate in this 
boiler? 

Ans. — Down from the top drum to the middle lower 
drum through special return water-tubes of large 
diameter, and from thence through the smaller tubes to 



53 QUESTIONS AND ANSWERS 

the side drums. From there the water passes up through 
the curved tubes to the upper portion of the top drum, 
where the steam is disengaged. 

Ques. 139. — Describe the Niclausse boiler. 

Ans. — The Niclausse boiler is made up of a series of 
slightly inclined tubes. These tubes are double, that is, 
one inside the other, and they are connected to the front 
header in such a manner that the colder water flows down 
the inside tubes and returns to the front between the two 
tubes when heated by the action of the fire and hot gases 
on the larger outside tubes. Each vertical row of tubes 
is connected at the front end to a separate header, the 
headers being placed side by side, and all leading into a 
top drum or steam-collector. 

Ques. 140. — How is the entermg feed-water at the 
front kept separate from the hot ascending currents of 
water? 

Ans. — By a diaphragm in the top drum that keeps the 
cooler water separate from the hot water and steam. 

Ques. 141. — How are the tubes connected to the 
headers in the Niclausse boiler? 

Ans. — By coned surfaces on the ends of the tubes 
bearing on similar coned surfaces in the headers, and kept 
in contact by outside dogs and nuts. These joints 
appear to cause no trouble by leakage. 

Ques. 142. — Is the Niclausse boiler much used? 

Ans. — It is used to some extent in the British navy, 
and also in several large United States war-ships. 

Ques. 143. — Of what type is the Normand boiler? 

Ans. — The Normand boiler is a marine water-tube 



THE BOILER 53 

boiler of the Thornycroft type. The two outer rows of 
tubes are formed into a wall of tubes, and in the vicinity 
of the furnace the tubes are arched upwards in order to 
form a combustion chamber. Back of the furnace the 

'Part front tfiew. ; Part section throicgh 
furnace. 




Fig. 26. The Normand Boii,sr» 



curvature is not so great, although all of the tubes are 
curved more or less, to permit of expansion when heated. 
Ques. 144. — ^What course do the gases take in this 
boiler? 



fa'4 



QUESTIONS AND ANSWERS 



Ans. — The gases proceed from the fire among the 
tubes, and traverse the length of the boiler to the rear 
end, where the}^ pass below a brick deflecting plate to 
the space surrounding those tubes that are less curved. 




Fig. 27. The Yarrow Boii^er. 

Ques. 145. — What other peculiar feature character- 
izes the Normand boiler? 

Ans.-^Provision is made for tne admission of air 
doove the fire. 



THE BOILER 55 

Ques. 146. — How is this accomplished? 

Ans. — By means of a small air casing at the front and 
back, and a series of small holes one inch in diameter lead- 
ing through the brickwork to the space above the fire. 

Ques. 147. — For what kind of service is the Normand 
boiler mainly adapted? 

Ans. — For torpedo-boat destroyers. 

Ques. 148. — What is the distinguishing feature of the 
Yarrow boiler, among boilers having water-tubes of small 
diameter? 

Ans. — The Yarrov/ boiler has straight tubes. It also 
has at the bottom on each side a small water-chamber or 
mud-drum with nearly flat tube-plates, into which the 
tubes are expanded. The tubes run in an inclined direc- 
tion from these water-drums to the steam and water- 
drum at the top. 

Ques. 149. In what manner does the water circulate 
in the Yarrow boiler? 

Ans. — Those tubes which receive the most heat con- 
duct the water from the lower drums to the upper drum, 
into which the steam is delivered. Other tubes which 
are cooler carry the water from the upper drum to the 
lower drums. 

Ques. 150. — Describe the Mosher boiler. 

Ans. — The Mosher boiler has two upper steam-drums 
and two lower and smaller water-drums, the water- 
drums being directly underneath the steam-drums. These 
drums are connected by curved generator pipes of small 
diameter, the pipes entering the steam-drums above the 
water-line. 



56 



QUESTIONS AND ANSWERS 



Ques. 151. — How does the water find its way from 
the upper to the lower drums? 

Ans. — By means of two external downtake pipes 
4 inches in diameter. The boiler is cased in, the casing 
being lined with fire-brick. 

Ques. 152. — For what class of service is the Mosher 
boiler mainly adapted? 

Ans. — Torpedo boats and high-speed yachts. 




Fig. 28. The Mosher Boiler. 



Ques. 153. — Describe the construction of the Almy 
boiler. 

Ans. — It is made principally of short lengths of pipe 
screwed into return bends and into twin unions. At the 
bottom there is a larger pipe or header that surrounds 
the two sides and back of the grates, and there is a 
similar structure at the top, the two headers being con- 
.fected by the smaller pipes. 



THE BOILER 



57 



Ques. 154.— How i^ fh^ ^ 




F'C. 29. The AiMY BonER. 






58 



QUESTIONS AND ANSWERS 



the separated water and the feed-water pass down 
through circulating pipes to the lower header, 

Ques. 155. — What other peculiar feature attaches to 
this boiler? 




Fig. 30. The Du Temple Boii^er. 



Ans. — It is provided with a coil feed-water heater 
above the main boiler. 

Ques. 156.— Describe in general terms the Du Temple 
boiler. 



THE BOILER 



59 



Ans. — It is of the same general character as the 
Thornycroft type, except that the generating tubes dis- 
charge into the steam-drum below the water-line. 

Ques. 157. — How are these tubes connected to the 
drums? 




Fig. 31. Reed's Boii^er. 



Ans. — By cones and nuts. 

Ques. 158. — Is the Du Temple boiler used to any 
great extent? 

Ans. — Yes; it is used extensively in the French navy, 
especially on vessels of the torpedo-boat type 

Ques. 159. — Describe Reed's boiler. 



60 



QUESTIONS AND ANSWERS 



Ans. — This boiler resembles the Du Temple boiler. It 
has the usual top collector drum, and two lower drums 
with curved g^enerating pipes connecting them. 

Ques. 160. — How are the tubes attached to the 
drums? 




Fig. Z2. The Seabury Boii^er. 

Ans. — By screwed connections at each end, with 
nuts inside the chambers. 

Ques. 161. — How are the gases caused to traverse 
the heating surface in this boiler? 

Ans. — By means of diaphragms fitted to the tubes. 

Ques. 162. — What class of service is this boiler 
largely used in? 



THE BOILER 61 

Ans. — British torpedo-boat destroyers, and also on 
third-class cruisers. 

Ques. 1G3. — Describe the Seabury boiler. 

Ans. — The Seabury boiler has three lower water- 
drums, the middle drum being smaller than the two out- 
side drums. These drums are connected to one large 
steam and w^ater-drum above by curved pipes of small 
diameter and the furnace is divided into two sections by 
the central nest of pipes. Above the boiler tubes and 
inside the casing there is a coil feed-water heater. 

Ques. 164. — Describe the latest type of Belleville 
boiler? 

Ans. — The Belleville boiler is a water-tube boiler, and 
is of extensive use on large ships. It is made up of two 
distinct series of straight tubes, larger in diameter than 
those of the curved type. These tubes are placed nearly 
horizontal, each alternate horizontal row being slightly 
inclined in the opposite direction to the row above it. 
The generator proper has a water-chamber below and a 
steam-drum or chamber on top, and the zigzagged tubes 
are connected to these respective chambers. 

Ques. 165. — What kind of a furnace has this boiler? 

Ans. — A rectangular brickwork furnace inclosed in a 
steel casing, and the generating tubes are placed directly 
over the grates, the bottom row of tubes being about two 
feet above the grates. Baffle plates are secured at inter- 
vals among the tubes for the purpose of causing the hot 
gases to traverse the whole of the heating surface. 

Ques. 166. — How is circulation of the water secured 
in the Belleville boiler? 



t)^ 



QUESTIONS AND ANSWERS 



Ans -By means of external return water-pipes, one 
on each s:de connecting the ends of the top drum with 
tH« lower water-chamber, the cooler water thus passing 



cftet /ed\ 
cconom. 




WiG.2i. Beti^EviiAE Boii^ER WITH E:coNOMisiau 



THE BOILER 63 

down through these pipes into the lower drum, and from 
thence the heated water passes up through the generating 
tubes, discharging into the top drum, where the steam is 
disengaged. 

Ques. 167. — What are the usual dimensions of the 
generating tubes? 

Ans. — Four and one-half inches in diameter and seven 
feet six inches in length. The ends are connected by 
being screwed into malleable cast-iron boxes. 

Ques. 168. — How is the economizer or feed-water 
heater attached to this boiler? 

Ans. — It is placed directly above the generator, a 
space called the combustion chamber being left between 
the two series of tubes. The tubes of the economizer are 
smaller, being 2^ inches in diameter. The general form 
of the economizer resembles that of the generator. 

Ques. 169. — What is the course of the feed-water in 
this boiler? 

Ans. — It enters the bottom of the economizer and is 
forced upwards to and fro through the zigzagged tubes 
to the top, and from thence it falls to the bottom of the 
hot water collector at the top, and then flows to the 
return pipes, through which it passes to the generator. 

Ques. 170. — Mention another peculiar feature of this 
boiler. 

Ans. — An automatic feed-regulating device worked 
by a float in a chamber acting upon the feed-valve. 

Ques. 171. — Is the Belleville boiler an economical 
boiler? 

Ans. — It is; an actual evaporation of from 9.3 poundj 



64 



QUESTIONS AND ANSWERS 



to 9.9 pounds of water per pound of coal having been 
obtained under test, with the feed-water at a temperature 
of 68 degrees. 

pipe- comnected^ to 
Vfper partof element 




view of* A 



iKft» ^4. Automatic Feed Regulator for Belleville Boiler. 



CHAPTER III 

BOILER CONSTRUCTION 

Ques. 172.— What is the best material to use in the 
construction of the shell of the boiler? 

Ans.— Open- hearth steel, having a tensile strength of 
from 55,000 pounds to 60,000 pounds per square inch. 

Ques. 173.— What is meant by the expression tensile 
strength (T. S.)? 

Ans.— The expression 60,000 pounds tensile strength 
means that it would require a pull of 60,000 pounds in 



r I I 



Moi/Z^Z^ 



M/.!f*:.._^^^^^„. 



Fig. 35. Test Piece. 

the direction of its length to break a bar of the material 1 
inch square, or 2 inches wide by K inch thick, or 2.67' 
inches wide by Yz inch thick. 

Ques. 174.— How are steel sheets for boiler construc- 
tion tested? 

Ans.— A small piece, called a test piece, is cut from 
each sheet and placed in a testing machine. 

Ques. 175.— What is the working test for steel boiler 
sheets? 

Ans. — A piece from each sheet is heated to a dark 

65 



66 



QUESTIONS AND ANSWERS 



cherry red, plunged into water at 60° temperature, and 
bent double cold under the hammer, such piece to show 
no flaw or crack after doubling. 

Ques. 176.— Of what material should the tubes of 
fire-tube boilers be made? 

Ans.— A good quality of homogeneous iron. 

Ques. 177. — What is the working test for boiler tubes? 

Ans. — They should show^ no flaw when expanded into 
the flue-sheet and beaded. 




^d^ > 




Fig. 36. Crow Foot Braces. 



Ques. 178. — What should the specifications be regard- 
ing rivets? 

Ans. — All rivet material should be of good charcoal 
iron, or mild steel, tough and soft. Test, a good rivet 
should bend double cold, without showing fracture. 

Ques. 179. — Of what material are the tubes of water- 
tube boilers usually made? 

Ans. — Of good charcoal iron or mild steel specially 
prepared for the purpose, and lap welded, or drawn. 



BOILER CONSTRUCTION 



67 



Ques. 180. — What is the test for tubes from 3/^ to 4 
inches in diameter and No. 10 wire gauge?^ 

Ans. — Apiece 1/4 inches in length is cut from one end 
of a tube, and this piece must stand hammering down cola 
vertically without showing a crack or split, when down 
solid. 

Ques. 181. — Of what material should stay-bolts be 
made? 

Ans. — Of iron or mild steel, especially manufactured 
for the purpose. 




Fig. 11, Gusset Stays. 

Ques. 182. — What should be the tensile strength of 
5tay-bolt material? 

Ans. — For iron, not less than 46,000 pounds; for steel, 
not less than 55,000 pounds. 

Ques. 183. — What kind of material are braces and 
stays made of? 

Ans. — The material for braces and stays should be of 
the same quality as the best stay-bolt stock. 

Ques. 184. — What is the object sought in staying the 
flat surfaces of a boiler internally? 

Ans. — The object is to strengthen those surfaces 
sufficiently to enable them to withstand the maximum 
internal working pressure to which thev will be subiected. 



68 



QUESTIONS AND ANSWERS 



Ques. 185. — Does the cylindrical portion of a boiler 
need bracing? 

Ans. — It does not, for the reason that the internal 
pressure tends to keep it cylindrical. 

Ques. 186. — What is the maximum direct pull per 
square inch of section that may be allowed on braces and 
stay-rods? 




Fig. 38. Through Stay Rous. 



Ans. — For iron, 6,500 pounds; for steel, 8,000 
pounds; and this point should be kept in view when spac- 
ing the braces. 

Ques. 187. — What is meant by spacing braces? 

Ans. — The distance from center to center that the 
stays are from each other at the point of their connection 
to the stayed surface. 

Ques. 188. — Give an example. 

Ans. — The stays in a certain boiler are spaced 8 inches 
Apart, center to center, therefore each stay suoports 



BOILER CONSTRUCTION 



69 



8 X 8=64 square inches. Assuming the working pressure 
to be 100 pounds per square inch, the sectional area of 
each stay should be 1 square inch. 




Fig. 39. V^RTiCAi, Tubular Boiler, with Submerged Tubes. 

Ques 189. — Suppose the working pressure is 250 
pounds per square inch and the stays are spaced 6 inches 



70 



QUESTIONS AND ANSWERS 



center to center, what should be the sectional area of each 
stay? 




Ans. — The pressure to be sustained by each stay would 
be 6x6 = 9000 pounds. Assume the stays to be of 



BOILER CONSTRUCTION 



71 



steel and unwelded, and allowing a direct pull of 7,200 
pounds per square inch, the sectional area of each stay 
should be flH — 1.25 square inches; or, if the stays are 
1.5 inches smallest diameter, and a direct pull of 8.000 
pounds per square inch of section is allowed, they may be 
spaced 7 inches, center to center. 

Ques. 190. — Of what forms are boiler stays usually 
made? 

Ans. — For low-pressure boilers, crow-foot stays; for 
high-pressure boilers, through stay-rods and gusset-stays. 




Fig. 41. Common Stay-Boi,T. 



Ques. 191. — Where are stay-bolts used? 

Ans. — In fire-box boilers, and all boilers of the loco- 
motive type, to tie the fire-box to the external shell. 

Ques. 192. — How are stay-bolts applied? 

Ans. — A continuous thread is cut on the stay-bolt rod, 
the same thread being also tapped in the holes in the 
external plate, and the inside sheet. The steel stay-bolt 
is then screwed through the plates and allowed to project 
far enough at each end to permit of its being riveted down 
cold. 



72 



QUESTIONS AND ANSWERS 



Ques. 193. — What is the principal cause of the break 
ing of stay-bolts? 

Ans. — The unequal expansion of the sheets into which 
they are screwed. 

Ques. 194. — Why are stay-bolts sometimes drilled 
partly through their length? 

Ans. — In order that, if the bolt breaks, the steam or 
water may blow out through the small hole and give 
warning of the break. 

Ques. 195. — Describe the Tate flexible stay-bolt. 





Fig. 42. Tate Flexible Stay Bolt. 

Ans. — The outer head is ball shaped, and is inclosed 
within a socket formed by a sleeve that screws into the 
outer sheet and a cap that screws onto the sleeve. The 
other end of the bolt is screwed into and through the fire- 
sheet a sufficient distance to allow of riveting. 

Ques. 196. — What is meant by the efficiency of a 
riveted joint? 

Ans. — It is the per cent, of strength of the solid plate 
that is retained in the joint. 

Ques. 197. — What is the efficiency of a properly 
proportioned double riveted butt-joint? 



BOILER CONSTRUCTION 



73 



Ans. — From 71 to 75 per cent. 

Ques. 198. — What is the efficiency of a properly pro- 
portioned triple riveted butt-joint with inside and outside 
welts or butt-straps? 

Ans. — From 85 to 88 per cent. 




Fig. 43. Tate Fi,exibi,e Stay-Bolt, Unthreaded. 

Ques. 199. — Where is the weakest portion of the triple 
riveted butt-joint? 

Ans. — At the outer row of rivets. 





Table 4 

Table of Diameters of Rivets* 


Thickness of 
Plate 


Diameter of Klvet 


Thickness of Plate 


Diameter of Rivet 


V4 inch 

»/l8 " 
% " 

V2 " 


V2 inch 
V16 " 
"/16 " 


%6 inch 

Vs " 
3/4 " 
% " 
1 


Vs inch 
«/ia " 

1V,6 " 

IVs " 
IV4 " 



*Machine design — W. C. Unwin. 

Ques. 200. — What percentage of efficiency may be 
retained in a properly designed quadruple riveted butt- 
joint having both inside and outside butt-straps? 
» Ans. — 94 per cent. 



?4 



QUESTIONS AND ANSWERS 



Ques. 201. — Where is the weakest portion of such a 
loint? 

Ans. — At the outer row of rivets. 




Fig. 44. Double Riveted Butt-Joint. 



Ques. 202. — How may boiler heads be constructed 
which will not require to be stayed? 

Ans. — By being dished, or '^bumped up." 




Fig. 45. Triple Riveted Butt-Joint. 



Ques. 203.— What is the depth of dish, as adopted by 
steel-plate manufacturers? 



BOILER CONSTRUCTION 



75 



Ans.^ — One eighth of the diameter of the head, when 
flanged. 

Ques. 204. — What should be the thickness of the head 
as compared to the thickness of the shell? 













i^« 



i ^^w 






Fig. 46. QuadrupIvE Riveted Butt-Joint. 



Lloyd's rules, condensed, are as follows: 
Lloyd's Rules — Thickness of Plate and Diameter of Rivets 



Thickness of 


Diameter of 


Thickness of 


Diameter of 


Plate 


Rivets 


Plate 


Rivets 


J^ inch 


^ inch 


^ inch 


% inch 


"Ae " 


5/8 " 


1%6 " 


Vs '' 


V2 " 


3/4 " 


Vs " 


1 " 


9/16 " 


Va " 


1%6 " 


1 " 


5/8 " 


Va " 


1 " 


1 '* 


m« " 


Vs " 







Ans. — The heads should be as thick, or slightly thicker, 
than the shell plate. 



76 



QUESTIONS AND ANSWERS 



Ques. 205. — What method other than riveting may 
be, and sometimes is employed in the formation of boiler 
seams? 

Ans. — Boiler seams may be welded if the material 
from which the plates are rolled is of the best, and great 
care and skill are exercised. 

Ques. 206. — Mention two of the advantages possessed 
by welded seams over riveted seams? 

Table 5 

Proportions of Triple-riveted Butt Joints with Inside and 
Outside Welt 



Thickness of 


Diameter of 


Pitch of 


Pitch of 


Efficiency 
Per Cent 


Plate 


Rivet 


Rivet 


Outer Rows 


Inches 


Inches 


Inches 


Inches 


% 


"/l6 


3.25 


6.5 


84 


Via 


"/l6 


3.25 


6.5 


85 


V2 


"/l6 


3.25 


6.5 


83 


«/l6 


% 


3.50 


7.0 


84 


% 


1 


3.50 


7.0 


86 


^4 


lVl6 


3.50 


7.0 


85 


% 


IVs 


3.75 


7.5 


86 


1 


IV4 


3.87 


7.7 


84 



Ans. — First, a good welded joint approaches more 
nearly to the full strength of the material than can 
possibly be attained by rivets, no matter how correctly 
designed the riveted joint may be; second, the welded 
joint, having a smooth surface inside the boiler, is much 
less liable to collect scale and sediment than is the riveted 
joint. 

Ques. 207. — Why should the longitudinal or side 
seams of a boiler be stronger than the girth or round- 
about seams? 



BOILER CONSTRUCTION 77 

Ans. — Because the force tending to rupture the boiler 
along the line of the longitudinal seams is proportional 
to the diameter divided by two, while the stress tending 
to pull it apart endwise is only one-half that, or propor- 
tional to the diameter divided by four. 

Ques. 208. — What is the formula for ascertaining 

the bursting pressure of a boiler? 

A TS X TX E T. . ^. ^ 
Ans. — ^^ =B, m which 

T S = Tensile strength 
T = Thickness of sheet 
E = Efficiency of joint 
R = Radius (one-half the 

diameter) 
B = Bursting pressure 
Ques. 209. — How is the safe working pressure of a 
boiler ascertained? 

Ans. — First calculate the bursting pressure, then 
divide this by the factor of safety, which usually is five, 
although in some instances a safety factor of eight is used. 
Ques. 210. — In addition to the regular bracing and 
staying, how are the heads of return tubular and Scotch 
marine boilers greatly reenforced? 

Ans. — By the tubes, which are expanded into the 
heads and beaded down on the ends. 

Ques. 211. — Are the tubes always expanded into the 
tube-sheets? 

Ans. — They are in fire-tube boilers. In some forms 
of water-tube boilers the tubes are screwed into the 
headers or chambers. 



78 



QUESTIONS AND ANSWERS 



yues. 212. — What type of furnace is largely used in 
internally fired boilers? 

Ans. — The Morison corrugated furnace. 

Ques. 213. — Mention three advantages gained by the 
use of corrugated furnaces. 

Ans. — First, the corrugations (if properly made) add 
great rigidity and strength to resist the crushing strain to 
which the furnaces are subjected; second, there is more 
heating surface in a corrugated than in a smooth surface; 
third, the alternate expansion and contraction of the 




Fig. 47. Section of Tube Expanded into Sheet. 

corrugated surface tends to loosen any scale that may 
form on the surface inside the boiler. 

Ques. 214. — In regard to riveted seams, which is the 
better method, to drill or to punch the rivet-holes? 

Ans. — The rivet-holes should be drilled. In good 
boiler work this method is now always followed. 

Ques. 215. — What other important point should be 
kept in view in joining the plates of a boiler? 

Ans. — To get the joint tight without caulking, or at 
least with as small an amount of caulkine as Dossible. 



BOILER CONSTRUCTION 79 

Ques. 216. — Mention some of the iuiurious eflfects of 
excessive caulking. 

Ans. — First, it is one of the most fruitful causes of 
grooving along the edges of the seams ; second, it tends 
to raise the edge of the plate that is caulked, thereby 
causing looseness at the joint. 

Ques. 217. — What other very important point should 
be secured in the construction of the boiler? 

Ans.— The rivet-holes in the plates should come fair 
before the rivet is put in. 



Fig. 48. Morison Corrugated Furnace. 

Ques. 218. — If the rivet-holes do not come fair what 
should be done with them? 

Ans. — They should be made exactly true by the use of 
a rimer. 

Ques. 219, — What should not be done with the rivet- 
holes in case they do not come fair? 

Ans. — They should not be drifted. A drift-pin is 
often the primary cause of starting a crack in a sheet. 

Ques. 220. — What can be said generally concerning 
the construction of a boiler, especially one intended for 
high pressures? 



80 QUESTIONS AND ANSWERS 

Ans. — Only the best material should be used, and 
great care and skill should be exercised in all the detail 
of assembling it. 

By reference to Chapter I, Part 2, of Swingle's 
* 'Twentieth Century Hand Book for Engineers and Elec- 
tricians," the student will be enabled to obtain much, 
more detailed information concerning boiler construction, 
the strength of riveted joints, bracing and staying, 
strength of material, etc., as all of these important feat- 
ures are dwelt upon at length and fully discussed. 



CHAPTER IV 

BOILER SETTINGS AND APPURTENANCES. 

Ques. 321. — What kind of a setting is requirea fof 
internally fired boilers? 

Ans. — First, a good solid foundation, second, the 
boiler should be covered with non-conducting, non-com- 
bustible material of some sort, to prevent radiation of 
heat, and the whole should be encased in a sheet-metal 
jacket. 





Fig. 49. P1.AN AND Elevation of Boii^er Setting, Showing Air Spaces. 

Ques. 222. — What kind of a setting is required for 
horizontal tubular and water-tube boilers? 

Ans. — Brick walls with an inner lining of fire brick. 
When the boiler is supported by lugs resting upon 
the walls, a heavy iron plate should be imbedded in the 
brickwork, for each lug to rest upon. The walls should 
also be tied together, both endwise and transversly, by 
iron rods not less than 1/4 inch in diameter, extending 
clear through in both directions, the bottom, rods to be 
laid in place as the walls are being built. These rods are 
to have a thread and nut on each end, and are secured 

81 



82 



QUESTIONS AND ANSWERS 



to heavy cast or wrought iron bars called buck stays, 
placed vertically against the outside of the walls. 

Ques. 223. — How may boiler walls be greatly pro- 
tected from the injurious action of the heat? 

Ans. — By leaving an air-space of 2 inches between the 
fire-brick lining and the outer wall, beginning at the 
level of the grate bars and extending as high as the cen- 
ter of the boiler. Above this height the walls should be 
solid. 



'4" 




Fig. 50. Clamp i?or Back Arch. 

Ques. 224. — What is the duty of bridge-walls and 
bafflers? 

Ans. — To present a hot surface for the unconsumed 
gases to impinge against, and also to divert the gases 
towards the heating surface of the boiler. 

Ques. 225. — How may a good and durable back arch 
for a horizontal tubular boiler be constructed? 

Ans. — Take flat bars of iron Yz inch thick by 4 inches 
i« width, cut them to the proper length, bend them to the 



BOILER SETTINGS AND APPURTENANCES 



83 



shape of an arch, and turn 4 inches of each end back at 
right angles. The clamp thus formed is to be filled with 
a course of side arch fire-brick, and will form a complete 
and self-sustaining arch 9 inches wide and with sufficient 
spring to cover the distance between the back wall and 
the back head of the boiler above the tubes. Enough of 
these arches should be made so that when laid side by 
side they will cover the distance from one side wall to 
the other, across the rear end of the boiler. 







Fig. 51. Back Arch Compi,ete. 

Ques. 226. — ^What advantages do this form of back 
arch possess over the ordinary fiat cover? 

Ans. — First, it can come and go with the expansion 
and contraction of the boiler; second, it always maintains 
a practically air-tight cover at this important point; 
third, in case of needed repairs to the back end of the 
boiler the sections may be easily removed, one at a time, 
and when the repairs are completed they may be reset with 
very small expense* 



84 



QUESTIONS AND ANSWERS 



Ques. 227. — Give an easy rule for ascertaining the 
dimensions of the grates. 

Ans. — For a horizontal tubular, the length of the 
grates should equal the diameter of the boiler. The 
width depends upon the construction of the furnace. If 
the fire-brick lining is built perpendicular, the width of 
grate will also equal the diameter of the boiler, but if 




Fig. 52. Back Arch in Pi^ace. 

Khe lining is given a batter of 3 inches, starting at the 
level of the grates, then the width of grate will be 6 
inches less. 

Ques. 228.— What is the ordinary ratio of grate sur- 
face to heating surface for land boilers, with natural 
draught? 

Ans. — One square foot of grate surface to every 36 
square feet of heating surface. 



BOILER SETTINGS AND APPURTENANCES 



85 



Ques. 229. — What ratio of grate surface to heating 
surface is usually chosen with forced draught? 

Ans. — One square foot of grate surface to 40 square 
feet of heating surface, and in some instances the ratio 
is as high as 1 to 50. 

Ques. 230. — How many different styles of grate-bars 
are in general use? 

Ans. — Four; first, the common stationary grate, 
consisting of a plain cast-iron bar tapered in cross 




PLAIN GRATE 

(SlViDAPD PATTERN) 




-SAW-DUST AND WOOD ©RATF 

Fig. 53. Grate Bars. 



section and having small projections cast on the sides to 
keep the bars apart a sufficient distance; second, herring- 
bone grates, consisting of channel-shaped cast-iron bars 
having V-shaped openings on top to allow the air to pass 
through to the fire; third, shaking or rocking grates, 
fourth, dumping grates. 

Ques. 231. — What percentage of the total grate area 
is usually allowed for the admission of air through the 
grates? 



86 



QUESTIONS AND ANSWERS 



Ans. — From 30 to 50 per cent, depending upon the 
kind of coal used. 

Ques. 232. — What is the heating surface of a boiler? 

Ans. — All the surtaces that are in contact with and 
covered by water on one side and surrounded by flame or 
hot gases on the other side. The areas of these surfaces 
are estimated in square feet and added together. 




Fig. 54. M'Ci^ave's Grates. 




Fig. 55. M'Ci^ave's Grates. 



Ques. 233. — Is it possible to estimate the horse-power 
of a boiler from its heating surface? 

Ans. — It is in a general way, but not accurately. 

Ques. 234. — How many square feet of heating surface 
are usually allowed per horse-power? 

Ans. — From 10 to 16 square feet, depending entirely 
upon the type of boiler. 

Ques. 235. — Give some examples. 



BOILER SETTINGS AND APPURTENANCES 87 

Ans. — For water-tube boilers 10 to 12 square feet of 
heating surface; for horizontal fire-tube, 12, for vertical 
fire-tube, 12 to 15, and for locomotive boilers, 12 to 16 
square feet of heating surface per horse-power. 

Ques. 236.— Why this difference? 

Ans. — Because the heating surface is more effective 
in some types of boilers than it is in others. 

Ques. 237, — What is the rule for calculating the heat- 
ing surface of a horizontal tubular boiler? 

Ans. — Taking the dimensions in inches, multiply two- 
thirds of the circumference of the shell by its length. 
Multiply the inside circumference of one of the tubes by 
its length, and this product by the number of tubes. Add 
these two products together, and to this sum add two- 
thirds of the combined areas of both tube-sheets and 
from this latter sum subtract twice the combined sec- 
tional areas of all the tubes. The result will be the 
heating surface in square inches, which, divided by 
144, will give the number of square feet of heating 
surface. 

Ques. 238. — What is the rule for finding the heating 
surface of vertical fire-box boilers? 

Ans. — Multiply the circumference of the fire-box by 
its height above the grate. Find the heating surface of 
the tubes by the process given in the former rule and add 
these two products together, and to this add the area of 
the lower tube sheet. From this sum deduct the sectional 
area of all the tubes. The dimensions having been taken 
in inches, the result should be divided by 144 to ascertain 
the number of square feet of heating surface. 



88 QUESTIONS AND ANSWERS 

Ques. 239. — Why is the inside circumference of the 
tubes taken? 

Ans. — Because in fire-tube boilers this is the portion 
that is directly exposed to the heat. 

Ques. 240. — Why are the combined sectional areas of 
the tubes subtracted from the area of that portion of the 
tube-sheets that is exposed to the heat, 

Ans. — Because the effective heating surface of a 
tube-sheet is the surface rem.aining after the areas of the 
openings through the tubes is deducted. 

Ques. 241. — What is implied in the expression **a 
3-inch boiler tube?" 

Ans. — It means a tube 3 inches in external diameter. 

Ques. 242. — Such being the case, which diameter 
should be considered m calculatmg the heating surface of 
fire-tubes? 

Ans. — Only the inside diameter, which equals the out- 
side diameter mmus twice the thickness of the tube. 

Ques, 243. — In calculating the heating surface of the 
tubes of water-tube boilers which diameter should be 
taken? 

Ans. — The outside diameter, for the reason that the 
outside circumference is exposed to the heat. 

Ques. 244. — How is the heating surface of a water- 
tube boiler ascertained? 

Ans. — Much depends upon the style of boiler. A 
general rule and one that will apply in all cases, is to 
multiply the outside circumference of one of the tubes by 
Its length, and this product by the number of tubes that 
are of a similar length and diameter. If there are vari- 



BOILER SETTINGS AND APPURTENANCES 



89 



ous sections of tubes of varvlng lengths, the heating 
surface of each section must be ascertained separately 
and the whole added together. To this sum must be 
added the combined areas of those portions of the headers 
that are directly exposed to the heat, having first deducted 
the sectional area of the tubes. All of those portions of 
the steam and water-drums that are directly exposed to 
the heat should be estimated as heating surface also. 




n 



o^qOoOo cPo^o^o o^Qon 



y..q 




Fig. 56 Door o^ a Bei.i,Evili«E Boiler. 

The door proper has an outer and inner plate, the former being a screen plate 
with edges open for the admission of air The door is perforated with holes at 
ihe lower part, through which the air is drawn, and the inner plate, which is of 
cast iron, is closed at the bottom, and has holes for the discharge of air at i:he 
top. When the fires are alight, there is a continuous current of air flowing into 
the furnace through these plates. 



Ques. 245. — What is the rule for ascertaining the 
heating surface of a Scotch boiler? 

Ans. — The grates being set in the large main flues, 
only one-half of each flue area is available as heating 
surface. The following rule applies: To one-half the 
combined area of the main flue add the area of one head 
between the grate and water-line, minus the total cross- 
section of the tubes, plus one-half the cross-section of 



90 



QUESTIONS AND ANSWERS 



main flues, plus the combined inside area of the tubes, 
plus the inside area of the combustion chamber. 

Ques. 246. — Give the rule for finding the heating^ 
surface of a corrugated flue. 

Ans. — Multiply the average inside diameter in feet by 
the length of the flue in feet, and this product by the 




Fig. 57. 
Shows another variety, the air being admitted through holes at the bottom of 
the wrought-steel door proper, a perforated inner cast-iron plate being fitted to 
shield the door. The wrought-steel furnace frame which carries the door also 
has an inner shield plate of cast-iron perforated with holes. 

constant 4.93. The result is square feet of heating 
surface. 

Ques. 247. — What is the duty of a safety valve? 

Ans. — To automatically relieve the boiler of all 
pressure above a certain prescribed working pressure by 
allowing the surplus steam to escape into the atmosphere. 

Ques. 248. — If a boiler had no safety valve, or if the 



BOILER SETTINGS AND APPURTENANCES 91 

safety valve should refuse to work, and all other exit 
from the boiler be closed, and heat continuously applied, 
what would be the result? 

Ans. — An explosion must of necessity occur. 



Fig. 58. Pop Valve. 

Ques. 249. — How many types of safety valves are 
in use? 

Ans. — Two; the lever safety valve, and the spring- 
pop safety valve. 

Ques. 250. — Which is the best adapted to all kinds of 
service? 

Ans. — The spring-loaded pop safety valve is, for the 



92 



OUESTIOXS AND ANSWERS 



reason that any inclination o^ ^-e boiler, such as that 
caused by the vessel's pitching dna rolling in a heavy sea, 
does not interfere with the working of a spring-pop valve, 




Fig. 59. Inside View of a Pop SaFETY Vai.vE. 

while on the other hand the leverage of a weighted lever 
valve decreases with any inclination of the boiler that 



BOILER SETTINl.S AND APrURTENANCES 93 

would momentarily put the lever in an inclined position. 

Ques. 251. — What is the United States marine rule 
for determining the area of lever safety valves for boilers? 

Ans- — **Lever safety valves to be attached to marine 
boilers shall have an area of not less than 1 square inch to 



Fig. 60. Triplex Pop Safety Valve. 

every 2 square feet of grate surface in the boiler, and the 
seats of all such safety valves shall have an angle of 
inclination of 45 degrees to the center line of their axis." 
Ques. 252. — What is the rule regarding spring pop 
safety valves? 



94 QUESTIONS AND ANSWERS 

Ans. — Three square feet of grate surface are allowed 
to each square inch of safety-valve area. 

Ques. 253. — What other and more reliable method is 
there of calculating safety-valve area? 

Ans. — The method by which the area of the valve is 
based upon the quantity of steam that the boiler is capable 
of generating. 

Ques. 254. — Why is this method more reliable? 

Ans. — For the reason that the rate of combustion 
varies greatly under different conditions, as, for instance, 
when forced draught is employed, a much higher rate of 
combustion is attained than is possible with natural 
draught. 

Ques. 255. — Do the standard rules given in answers 
251 and 252 hold good for safety-valve areas for all 
pressures? 

Ans. — No; because the rate of efflux for steam 
increases as the pressure increases. Therefore, for the 
higher pressures the total safety-valve area may be 
reduced. 

Ques. 256. — What should be the lift of a safety valve 
in order to allow the proper area of escape? 

Ans. — One-fourth of the diameter of valve. 

Ques. 257. — What is the rule for ascertaining the 
pressure at which a lever safety valve will lift when the 
weight and its distance from the fulcrum are known, as 
also the effective weight of the valve, stem, and lever? 

Ans. — Multiply the weight by its distance from the 
fulcrum. Multiply the weight of the valve and lever by 
the distance of the stem from the fulcrum^ and add to the 



BOILER SETTINGS AND APPURTENANCES 95 

former product. Divide the sum of the two products by 
the product of the area of the valve multiplied by its dis- 
tance from the fulcrum. The result will be the pressure 
in pounds at which the valve will lift. 

Ques. 258. — What is the rule for finding the distance 
that the weight should be placed from the fulcrum for a 
required pressure? 

Ans. — Multiply the area of the valve by the pressure 



Fig. 61. Davis Bei^t Driven Feed Pump. 

at which it is desired to have it lift, and from this product 
subtract the effective weight of the valve and lever. 
Multiply the remainder by the distance of the stem from 
the fulcrum, and divide by the weight. The quotient will 
be the required distance. 

Ques. 259. — What is the rule for ascertaining the 
weight required when all of the other factors are known? 



96 



QUESTIONS AND ANSWERS 



Ans. — Multiply the area of the valve by the pressure, 
and from the product deduct the effective weight of the 
valve and lever. Multiply the remainder by the distance 
of the stem from the fulcrum and divide by the distance 
of the ball or weight from the fulcrum. The quotient 
wiU be the required weight in pounds. 







Fig. 62. Phantom V^iew o^ Marsh Independent Steam Pump. 

Ques. 260. — What can be said in general regarding 
the safety valve? 

Ans. — It is one of the most useful and important 
adjuncts of a steam boiler, and if neglected, serious 
results are apt to follow. 

Ques. 261. — Mention the two standard methods of 
supplying the feed-water to boilers under pressure? 

Ans. — First, by the feed-Dump; second, by the 
injector. 



BOILER SETTINGS AND APPURTENANCES 97 

Ques. 262. — What advantage has the feed-pump over 
the injector? 

Ans. — The advantage of being able to draw its supply 
of water from a heater, in which the exhaust steam is 
utilized for heating the feed-water before it enters the 
boiler. Great economy in fuel is thereby effected. 

Ques. 263. — What is a duplex pump? 

Ans. — A duplex pump consists of two steam-cylinders 
and two water-cylinders, each having the necessary 
pistons and valves. The steam-valves of one side are 




Fig. 63. Worthington Dupi^ex Boilkr Feed Pump. 

operated by the other side, and vice versa. Both water 
cylinders discharge into the same main. A common 
suction main serves both water-cylinders also. 

Ques. 264. — If one side of a duplex pump becomes 
disabled from any cause, how may the other side be 
operated for the time being? 

Ans. — Loosen the nuts or tappets on the valve-stem of 
the broken side and place them far enough apart so that 
the steam-valve will be moved through only a small por- 
tion of its stroke, thereby admitting only steam enough to 
move the empty steam-piston and rod, and thus work the 



98 



QUESTIONS AND ANSWERS 



steam-valve of the remaining side. The packing on the 
piston-rod of the broken side should be screwed up 
tightly, so as to create as much friction as possible, there 
being no resistance in the water end. In this manner the 
pump may be operated for several days or weeks, and 
thus prevent a shut-down. 




SUCTION 

Fig. 64. The Hancock Inspirator. 



Ques. 265. — How is the velocity of flow, or piston- 
speed per minute of a pump ascertained? 

Ans. — Multiply the number of strokes per minute by 
the length of stroke in feet, or fractions thereof. This 
will give the piston-speed in feet per minute. 

Ques. 266. — How is the velocity of flow In the dis- 
charge-pipe ascertained? 

Ans. — Divide the sauare oi the diameter of the water- 



BOILER SETTINGS AND APPURTENANCES 



^^ 



cylinder in inches by the square of the diameter of the 
discharge-pipe in inches, and multiply the quotient thus 




obtained by the piston-speed in feet per minute of the 
pump. 

Ques. 367, — When the velocity in feet oer minute is 



100 QUESTIONS AND ANSWERS 

known, how may the number of cubic feet discharged 
per minute be ascertamed? 

Ans. — Multiply the area of the pipe in square inches 
by the velocity in feet per minute, and divide by the con- 
stant 144. The result will be the number of cubic feet of 
water or other fluid discharged per minute. 

Ones. 268. — How may the required size and capacity 
of feed-pump for a certain boiler be ascertained? 



Fig. 66. The Self-Acting Injector, 

Ans. — Multiply the number of square feet of grate 
surface by the number of pounds of coal it is desired to 
burn per hour per square foot of grate. This will give 
the total coal consumed per hour, which, multiplied by the 
number of pounds water evaporated per pound of coal 
will result in the total number of pounds water required 
per hour. 

Ques. 269. — How may the required size of the feed- 
pump be ascertained from the number of square feet of 
heating surface? 



BOILER SETTINGS AND APPURTENANCES 



101 



Ans. — Allow a pump capacity of 1 cubic foot of watei 
per hour for each 15 square feet of heating surface. 

Ques. 370. — How can an injector lift and force watei 




into the boiler against the same or even higher pressure 
than the pressure of the steam supplied to the injector? 

Ans. — An injector works because the steam imparts 
sufficient velocity to the water to overcome the pressure 
in the boiler. 



102 



QUESTIONS AND ANSWERS 



Ques. 271. — What is the velocity of a jet of steam 
under 180 pounds pressure issuing from a nozzle? 

Ans. — About 3,600 feet per second. 

Ques. 272. — What is the velocity of a jet of water 
under a pressure of ISO pounds issuing from a nozzle? 




Ans. — Only 164 feet per second. 

Ques. 273. — Why does the steam have so much 
greater velocity than the water, when the pressure in both J 
instances is the same? 



BOILER SETTINGS AND APPURTENANCES 



103 



Ans. — Because of the latent heat that is stored in the 
steam. 

Ques. 274. — What is the purpose of the combining 
tube in an injector? 

Ans. — To bring the jet of steam and the jet of water 
into close contact in order that the steam may be con- 




WATER 
CONNECTIOH' 



Fig. 69. Water Column. 

densed and the size of the jet reduced sufficiently to allow 
it to enter the delivery tube, which is of smaller diameter 
than the combining tube. 

Ques. 275. — What is the velocity of the combined jet 
of water and condensed steam as it leaves the combining 
tube and enters the delivery tube, assuming the steam- 



104 QUESTIONS AND ANSWERS 

pressure in the boiler to be 180 pounds per square 
inch? 

Ans. — 198 feet per second. 

Ques. 276. — What velocity is actually needed to cause 
I the jet to enter the water-space of the boiler carrying 180 
pounds pressure? 

Ans. — Only 164 feet per second. The excess of 
34 feet per second imparted to the velocity of the jet 
serves to overcome the friction of the feed-pipe and 
the resistance of the main check-valve. 

Ques. 277. — In general terms, then, to what is the 
action of the injector due? 

Ans. — The action of the injector is due to the high 
velocity with which a jet of steam strikes the water enter- 
ing the combining tube, imparting to it its momentum 
and forming with it during condensation a continuous jet 
of smaller diameter, having sufficient velocity to over- 
come the pressure in the boiler. 

Ques. 278. — What is the object in fitting a boiler with 
a check-valve in the feed-pipe? 

Ans. — A check-valve is for the purpose of preventing 
the water in the boiler from backing up into the feed 
main and feed-pump. 

Ques. 279. — Where should the check-valve be located? 

Ans. — In the feed-pipe, as near to the boiler as 
possible. 

Ques. 380. — For what purpose are gauge-cocks and 
water-gauge glasses? 

Ans. — They are for the purpose of indicating the 
heieht of the water in the boiler while it is under pressure. 



BOILER SETTINGS AND APPURTENANCES 



105 



Ques. 281. — Describe the construction and operation 
of a glass water-gauge? 

Ans. — A water-gauge, otherwise known as a water 
column or combination, is a cast-iron or brass cylinder 
connected to the steam-space of the boiler at the top, and 
to the water-space near the bottom. The normal position 
of the safe water-level is near the middle of the water- 





Fig. 70. Ivow Water Ai^arm. 



Fig. 71. Combined High and 
Low Water Alarm. 



column, into one side of which are screwed brass fittings 
for the glass tube or water-glass, which is a strong tube 
of special manufacture. Each end of this tube passes 
through a stuffing box in the brass fittings. The joint 
is made steam tight by a rubber ring that fits around 
the tube and is compressed by a follower screwed onto it. 
The fittings that connect the water-column with the boiler 
are, or at least should be, equipped with automatically 
closing ball valves which will act in case the gauge-glass 
breaks. 



106 QUESTIONS AND ANSWERS 

Ques. 282. — Where are the gauge-cocks or test-cocks 

usually connected? 

Ans.— -They are usually connected to the water-column 
cylinder in such a position that the lowest one is at the 
desired water-level, one a few inches above that, and the 
third near the highest point of the heating service. These 
test-cocks should be opened several times a day in order 
to keep them clear for use in case the gauge-glass breaks. 

Ques. 283. — What is liable to happen to the water- 
column? 

Ans. — Unless the water and sediment are frequently 
blown out of it through the valve at the bottom provided 
for this purpose, the tubes and connections will become 
clogged, thus preventing a free circulation of the water, 
and the true w^ater-level in the boiler will not be indicated 
as it should be. 

Ques. 284. — What is a fusible plug? 

Ans. — A fusible plug is a 1-inch brass pipe threaded 
plug, having its center drilled out to a diameter of not 
less than /^ inch, and the hole filled with Banca tin or 
other fusible metal. 

Ques. 285. — Where should a fusible plug be attached 
to a boiler? 

Ans. — -A fusible plug should always be attached to 
that portion of the boiler that is first liable to become 
overheated on account of the water-level becoming too 
low. 

Ques. 286. — Mention some proper locations for fusible 
plugs in various types of boilers? 

Ans. — The back head of a horizontal tubular boiler, 



BOILER SETTINGS AND APPURTENANCES 



107 




about 3 inches above the top row of tubes, the crown- 
sheet of a horizontal fire-box boiler; the lower tube-sheet 
of a vertical boiler, or sometimes in one of the tubes a 
few inches above the tube-sheet; in the lower side of the 
upper drum of a water-tube boiler. The fusible metal 
which fills the center of the plug is of con- 
ical form in order to prevent its being blown 
out by the pressure behind it. On the other 
hand, the melting point of this fusible metal 
is such that when the water falls below it, 
and the steam under pressure in the boiler 
comes in contact with it, the metal is melted 
and runs out, thus allowing the steam to 
escape through the hole and give the alarm. 
If the melted plug is located in the crown- 
sheet of a fire-box boiler, the escaping 
steam and water will 
quench the fire and 
thus lessen the danger 



Fig. 72a. 

Klinger's Water Gauge Mounting.-The usual round thin gauge glasses 
give trouble with high-pressure steam, owing to frequent fractures, while the 
water level is often indistinct. Klinger's glass, designed to obviate these defects, 
gives promise of success. It consists of a thick fl t glass, with smooth front 
and serrated back, shown in section Fig. 12. a and b, the front and back of the 
mounting, are bolted together with the glass and packing, shown by thick lines, 
between them. The serrations, when clean, cause the water to appear black, 
as in Fig. 72a. 



Ques. 287. — For what purpose is a steam-gauge 
attached to a boiler? 

Ans. — For the purpose of indicating the number of 
pounds pressure per square inch in the boiler. 



108 



QUESTIONS AND ANSWERS 



Ques. 288. — What type of steam-gauge is in most 
general use? 

Ans. — The Bourdon spring tube gauge. 

Ques. 289. — Describe the construction of this gauge^ 
and the principle upon which it operates? 

Ans. — The Bourdon gauge consists of a thin, curved, 




^ 



FiG. 73. Auxiliary Spring Pressure Gacge. 

flattened metallic tube closed at both ends and connected 
to the steam-space of the boiler by a small pipe bent at 
some portion of its length into a curve or circle that 
becomes filled with water of condensation, and thus pre- 
vents the live steam from coming directly in contact with 
the tube or spring, while at the same time the full 



BOILER SETTINGS AND APPURTENANCES 109 

pressure of steam in the boiler acts upon the tube, tending 
to straighten it. The end or ends of the spring tube 
being free to move, and connected by a suitable geared 
rack and pinion with the pointer of the gauge, causes it 



Fig. 74. Auxiliary Spring Pressure Gauge, Sectionai. View. 

to move across the face of the dial, thus indicating the 
pressure of the steam in povmds per square inch on the 
inner surface of the boiler. When there is no pi^essure 
in the boiler the pointer should stand at 0. 



110 



QUESTIONS AND ANSWERS 



Ques. 290. — How should steam-gauges be cared for? 

Ans. — They should be tested frequently by comparing 
them with a gauge that has been tested against a column 
of mercury. 

Ques. 291.— How should the steam-space of the boiler 
be connected to the main steam-pipe or header? 

Ans. — There should be a steam stop-valve placed in the 
connection between the boiler and the header. The valve 




Fig. 75. Section ai. View American Pressure Gauge. 



used for this purpose is usually an angle-valve, and 
should be constructed so as to close automatically, 
especially in a battery of two or more boilers. 

Ques. 292. — Why should this valve be self-closing in 
case the pressure in the header is higher than the pressure 
in the boiler? 

Ans. — In order that in case of an accident to one of a 
battery of boilers the steam may be prevented from pass- 
ing out of the neader and into the disabled boiler. 



BOILER SETTINGS AND APPURTENANCES 



111 



Ques. 293. — Describe the construction and operation 
of an automatic steam stop-valve. 

Ans. — The valve is opened and closed by means of a 
screw-stem passing out through the stuffing box, and 
fitted with a hand-wheel outside. In large-size valves this 
screw-thread is carried in a strong yoke outside the cas- 
ing. The pressure from the boiler is on the under side of 

the valve-disk, thus tending 
to open it. The stem or 
spindle is independent of the 
valve, and is hollow to allow 
a smaller size sliding spin- 
dle connected to the valve 
to pass into it. This spin- 
dle serves to guide and hold 
the valve steady, while at 
the same time the valve is 
free to close automatically 
any time that the pressure 
in the main exceeds the 
pressure in the boiler. 

Ques. 294.— How is the 
steam admitted to the 
whistle or the steam siren? 

Ans. — Through a special stop-valve, usually of the 

self-closing type, being worked by a spring on the valve. 

Ques. 295. — Describe the action of the steam whistle. 

Ans. — The steam whistle produces its sound by the 

vibrations of a thin stationary metallic cylinder, under 

the impact of the steam. 




Fig. 76. Section of an Angi^e 
Stop-Vai.ve. 



112 



QUESTIONS AND ANSWERS 



Ques. 296. — How does the steam siren produce its 
sound? 

Ans. — By means pf the rotations of a small slotted 
wheel which in turning opens and closes narrow slots in 
the casing. 

Ques. 297. — How may the 
passage of water from the 
boiler into the steam-pipe be 
prevented to a large extent? 

Ans. — By means of an in- 
ternal pipe-extension called a 
dry pipe, that collects the 
steam from all parts of the 
steam-space through narrow 
slots on its upper side. The 
shape of these slots has a 
straining action on the steam. 

Ques. 298.— What is the 
object in equipping a boiler 
with a surface blow-off? 

Ans. — In order that it may 
catch and pass off impurities, 
such as grease, oil, and scum, 
floating on the surface of the 

y^2ilQY ^^^* ^^' ^'^^^^ F0G-WhISTI,E. 

Ques. 299. — Describe the construction and operation 
of the surface blow-off. 

Ans. — It is connected to the boiler near the water- 
level, and carries an internal pipe-extension that ends in a 
flat D'an, directly below the water-line. It should be 




BOILER SETTINGS AND APPURTENANCES 



113 



opened quite frequently, especially when muddy water is 
being fed to the boiler. This will allow the accumulated 
scum to pass out. 




Fig. 7o. Section of a Steam Siren. 

Ques. 300. — Where and how should the bottom blow- 
off be connected? 

Ans. — The bottom blow-off should be connected to 
the lowest section of the boiler, and should be fitted with 



114 



QUESTIONS AND ANSWERS 



pas; 

lie 
=^ 



|5 



A. 



a straight-way valve, or a cock, in order that there may 
be no obstruction to the free passage of the mud and other 
sediment when the boiler is being cleaned. 

Ques. 301. — For what purpose is the h^^drometer-cock, 
and where is it located? 

Ans. — In the marine serv- 
ice the water used in the 
boilers is more or less impreg- 
nated with solid matter, and it 
becomes necessary to test the 
density of the water in the 
. boilers at certain intervals. 
The hydrometer- cock is for the 
purpose of drawing off a 
quantity of water from the 
boiler for testing, and is fitted 
to the water-space of the 
boiler. 

Ques. 302.— Describe the 
construction and use of the 
hydrometer. 

Ans. — It is an instrument 
having a long, slender stem, 
made of either glass or metal. 
There are two bulbs in the stem. The smaller one is 
loaded and the larger one is hollow and filled with air, 
which gives the instrument buoyancy, and keeps it in a 
vertical position. The stem is graduated in degrees, each 
degree representing the presence of one-tenth the solid 
matter in sea-watcr. 




5<= 



Fig. 79. Hydrometer. 



BOILER SETTINGS AND APPURTENANCES 115 

Ques. 303. — What prooortion of sea-water is solid 

matter? 

Ans. — One thirty-second part. 

Ques. 304. — Upon what principle are the readings 
taken from the hydrometer based? 

Ans. — Upon the principle that when any body floats 
freely, the weight of the liquid displaced is equal to the 
weight of the body floating, so that the higher the density 
of the liquid the less depth will the body sink in it. If the 
instrument sinks only to the zero mark on the scale, the 
water is fresh: if it sinks to 10 degrees, it indicates the 
presence of one-thirty-second part of solid matter, and 
if it sinks to 40 degrees, it indicates a density caused by 
the presence of four times as much solid matter as there 
is in sea-water. 

Ques. 305. — How is the water in the boiler tested 
with the hydrometer? 

Ans. — A quantity of water is drawn off through the 
hydrometer-cock, fitted for this purpose into a long pot, 
into which the instrument is inserted. 

Ques. 306. — How are boiler hydrometers graduated, 
with reference to temperature? 

Ans.— They are usually graduated to suit a tempera- 
ture of 200 degrees Fahrenheit, as that is about the temp- 
erature of the water a few seconds after being drawn off 
for testing. 

Ques. 307. — How are the expansion and contraction 
of steam-pipes provided for? 

Ans. — In the smaller sized pipes a bend can be put in 
the length of pipe that will answer the purpose, but in the 



no 



QUESTIONS AND ANSWERS 



large pipes an expansion joint, having a stuffing box for 
the pipe to slide in and out of the adjacent pipe is fitted. 

Ques. 308.— Why is it 
necessary to place a sepa- 
rator in the line of pipe 
leading from the boiler to 
the engine? 

Ans. — The object of a 
separator is to provide an 
additional safeguard against 
priming, by preventing any 
water in the steam-pipe 
from entering the cylinder. 
Ques. 309. —Describe 
the ordinary separator. 

Ans. — It is a metal cyl- 
inder larger in diameter 
than the steam-pipe, and 
connected to the pipe near 
the engine, by flange con- 
nections in such a manner 
that the larger portion of 
the separator hangs in a 
vertical position below the 
pipe. It is divided from the 
top nearly to the bottom by 
a diaphragm, and the steam 
Fig. 80. Expansion Joint. enters on One side, near to 

the top, and impinges against the diaphragm, passes 
underneath it, and out on the other side near the top. 




BOILER SETTINGS AND APPURTENANCES 



117 




Any water that reaches the separator is mostly left 
at the bottom, only the steam passing on to the engine 
cylinder. A valve is provided at the bottom of the 
separator for drawing off the water. The height of the 
water in the separator is shown by a glass gauge. 

Ques. 310. — Describe the automatic steam separator. 

Ans. — In addition to the 
usual diaphragm, it is fitted 
with an automatic blow-out 
apparatus, having a float that 
is raised as the water accumu- 
lates, and which by a system 
of levers opens a valve of 
large area for drainage. The 
automatic separation also has 
a hand blow-off valve. 

Ques. 311.— What is an 
asbestos-packed cock, and 
where is it used? 

Ans. — An asbestos-packed 
cock has its top and bottom 
glands packed with asbestos, 
while the shell also has longi- 
tudinal grooves found in it which are packed with 
asbestos. These cocks are very suitable to use on boilers 
and steam piping where high pressures are carried, and 
at locations where cocks are more convenient than valves 
would be. 

Ques. 312. — ^What are funnel dampers, and for what 
purpose are they attached? 




Fig. 81. Separator. 



118 



QUESTIONS AND ANSWERS 



Ans. — They are hinged dampers fitted in the uptakes 
leading from the boilers to the funnel, in order that each 



'SiEUfmisr 




smt mr 



^ncf*i£C6 



eL0W0FfV»iV9 



Fig. 82. Automatic Separator. 



boiler may be shut off f rem the draught when not in use, 
and they are also for use when the fires are being cleaned. 



BOILER SETTINGS AND APPURTENANCES 



119 



These dampers should be fitted so thaj there are no means 
of closing them permanently, but that if released they will 
at once assume the open position. 

Ques. 313. — What are funnel stays? 

Ans. — Wire ropes carried from the top of the funnel 
to the ship's sides, and fitted with adjusting screws for 
the purpose of regulating the strains. 




Fig, 83. Asbestos-Packed Cock. 

Ques. 314. — What precautions should be taken with 
these stays before raising steam in the boilers? 

Ans. — The adjusting screws should be slackened in 
order to allow for the expansion in the length of the funnel 
as it becomes heated. 

Ques. 315. — What is the usual height of the funnels of 
modern vessels? 

Ans. — Ninety to 100 feet, measured i^rom the furnaces. 



120 



QUESTIONS AND ANSWERS 







^ 



;; Trz:-""r-]i-;.:i:::.z7- 




Fig. 84. Section of Armored Cruiser, Showing Stoke-hold 

AND Funnels. 



BOILER SETTINGS ANP APPURTENANCES 



121 



Ques. 316- — For what purpose is the funnel cover? 
Ans. — It is fitted over the top of the funnel for use 




Fig. 85. Section o^ Armored Cruiser, Showing 
Air Screen and Coal Bunker. 



122 QUESTIONS AND ANSWERS 

when the ship is in harbor, or if any of the funnels are not 
in use, in order to prevent rain-water from entering and 
corroding the uptakes. These covers are kept a little 
above the top of the funnel, in order to allow sufficient 
space for the escape of smoke from small fires used for 
airing and warming the boilers while they are lying 
idle. 

Ques. 317. — How is the stoke-hold of a steamer 
ventilated? 

Ans. — When natural draught only is used, screens 
are required to keep the downward current of cool air 
separate from the upward current of warm or vitiated 
air, otherwise the circulation will not be as good as it 
should be. 

Ques. 318. — When forced draught is employed for the 
furnaces, how is the air supplied? 

Ans. — One of the oldest and at the same time most 
expensive methods is to admit a jet of high-pressure 
steam directly from the boilers to the base of the funnel. 
This is known as the steam blast. Another plan of 
using the steam blast is to admit small jets of steam into 
the furnace, over the fire. 

Ques. 319. — What other principal plans for creating 
forced draught are employed? 

Ans. — First, admitting jets of compressed air into the 
base of the funnel, in a manner similar to the steam- jet; 
second, fitting a centrifugal fan in the uptake; third, 
blowing the air into closed ash-pits; fourth, closing the 
stoke-hoJd and keeping it filled with slightly compressed 
air. 



BOILER SETTINGS AND APPURTENANCES 



123 



Ques. 320. — Of the plans lust mentioned, which one is 
probably the most efficient? 

Ans. — Closed stoke-holds, although the third plan, 
viz., blowing the air into closed ash-pits, is an efficient 
method, but a certain degree of danger attaches to it, on 
account of the pressure in the furnaces being greater 




Fig. 86. Cross Section of Stoke-hold, Showing Air Lock. 



than that in the stoke-hold, and unless proper precautions 
are taken before opening the furnace doors for the pur- 
pose of replenishing the fires, the flames may be blown 
into, the stoke-hold and serious results follow. 

Ques. 321. — Is this latter system of closed ash-pits 
much in vogue? 



124 



QUESTIONS AND ANSWERS 



Ans. — It is used to a large extent in the United States 
navy, also many ships of the mercantile marine service. 
The British and other navies also use it to some extent. 

Ques. 322. — How may this system of creating a forced 
draught be made safe, so as to guard against the flame 
being blown into the stoke-hold? 




Fig. 87. Elevation of Stoke-hold, Showing Air lyOCK. 



Ans. — By fitting a device that automatically closes 
the air-supply to the ash-pit when the furnace door is 
opened for firing. 

Ques. 323. — What is the object of providing air-locks 
in the hold of a vessel? 



} 



J 



BOILER SETTINGS AND APPURTENANCES 



135 



Ans. — In order to provide for passage to and from 
the stoke-holds, when under pressure. 

Ques. 324.-— Describe the construction and operation 
of an air-lock? 

Ans. — An air-lock consists of a small air-tight cham- 
ber fitted with two hinged doors opening against the air 




See's Ash Kjector. 



In this apparatus, which is fitted in many large passenger steamers in which 
the raising of ashes on deck is objectionable, the ashes are placed in a trough 
leading to a pipe, a jet of water at a pressure of about 200 pounds per square inch 
from one of the pumps is then admitted, and scours the ashes along the pipe into 
the sea. A small valve is fitted to permit the entry of air into the pipe during 
the discharge. The apparatus is simple and efficient. 



126 



QUESTIONS AND ANSWERS 



pressure. In passing through only one door is open at a 
time which makes it possible to enter or leave the stoke- 
hold without allowing much air to escape and thus reduce 
the air-pressure in the stoke-hold. 

Ques. 325. — At what places aboard a ship are air-locks 
necessary? 



M i^]14|i^]L ^ 



B r B ^T ^ =w^ 



^S 



PnF^ 



^ 




^fnrta 



Fig. 89. Shaking Grates. 

Ans. — At all places where communication is had 
between the compartments under pressure and any other 
part of the ship. 

Ques. 326. — What are the advantages in general 
possessed by closed stoke-holds over other systems? 

Ans. — First, a reduction in the space and weight 



BOILER SETTINGS AND APPURTENANCES 127 

required by the boilers, since, by the addition of fans and 
screens, which are light and inexpensive, and supply the 
necessary air under pressure to the furnaces, the boilers 
may be made to develop from 20 to 25 per cent more 
power, than they would with natural draught; second, by 
the employment of blowing fans, a continuous supply of 
fresh air in the stoke-hold is assured and the health and 
comfort of the men working there is much better provided 
for than it would be with natural draught. 

Ques. 327. — How are the ashes raised from the stoke- 
hold to the deck, to be thrown overboard? 

Ans. — By means of the ash-tube and engine; the ash- 
tube leading from stoke-hold to deck, and the engine 
raising the ashes in an ash-bucket, that passes through 
the tube. Another method is by means of the ash-ejector, 
which is simply an inclined tube running from the stoke- 
hold to above the water-line, and overboard. At the 
lower end of this tube is a hopper, into which the ashes 
are shoveled, and at the bottom of this hopper they are 
picked up by a jet of water of high velocity, and forced 
through the inclined tube overboard. 



CHAPTER V 

BOILER OPERATION 

Ques. 328. — What should be the first care of as 
engineer, or water-tender, when he goes on watch? 

Ans. — He should ascertain the exact height of the 
water in his boilers by opening the valve in each of the 
drain-pipes of the water-columns, allowing it to blow out 
freely for a few seconds, then closing it tight, and allowing 
the water to settle back in the glass. 

Ques. 329. — What is one of the important dut es of 
the firemen coming ofif watch? 

Ans. — They should have the fires clean, the ash-pits 
all cleaned out, a good supply of coal on the floor, and 
everything in good condition for the oncoming force. 

Ques. 330. — What implements are needed for success- 
fully and quickly cleaning a fire? 

Ans. — A slice-bar, a fire-hook, a heavy iron or steel 
hoe, and a lighter hoe for cleaning the ash-pit. 

Ques. 331. — How may these tools be made, so that 
they will be light and easy to handle and at the same 
time strong and durable? 

Ans. — After the working ends have been fashioned to 
the desired shape, let each be welded to a bar of 1-inch or 
l/^-inch round iron 10 or 12 inches in length. Then 
take pieces of 1-inch or 1/4 -inch iron pipe, cut to the 
length desired for the handles, and weld the shanks of the 
tools to one end of the pipe handles and to the other end 

129 



BOILER OPERATION 12i^ 

weld a ring handle or a short cross-bar to facilitate hand- 
ling the tools. 

Ques. 332. — When a fire shows signs of being foul 
and choked, what should be done at once? 

Ans. — Prepare to clean it by allowing one side to burn 
as low as possible, putting fresh coal on the other side 
alone. 

Ques. 333. — Describe the process of cleaning a fire. 

Ans. — When the first side has burned as low as it can, 
without danger of letting the steam-pressure drop too low, 
take the slice-bar and shove it in along the side of the fur- 
nace, on top of the clinker, and back to near the bridge- 
wall, then, using the door-jamb as a fulcrum, give it a 
quick, strong sweep across the fire, and the greater 
portion of the live coals will be pushed over to the other 
side. What remains of the coal not yet consumed can be 
pulled out upon the floor with the light hoe and shoveled 
to one side, to be thrown back into the furnace after the 
clinker is removed. Having thus disposed of the live 
coal, take the slice-bar and shove it in on top of the 
grates, under the clinker, loosening and breaking it up, 
after which take the heavy hoe and pull it all out upon 
the floor, where the intense heat contained in the clinker 
should be quenched by a helper, with a pail of water, or 
water discharged from a small rubber hose. 

Ques. 334. — Having gotten one side of the fire cleaned, 
what is the next move? 

Ans. — Close the door for that side, and with the slice 
bar in the other side, push all the live coal over to the side 
just cleaned, where it should be leveled oflf, and fresh coal 



130 QUESTIONS AND ANSWERS 

added. After this has become ignited treat the other 

side in the same manner. 

Ques. 335. — Can a definite code of rules for Hand firing, 

be laid down, that will suit all conditions? 

Ans. — No; owing to the fact that there are so many 
different varieties of coal, some of which need very little 
stirring or slicing, while others, that have a tendency to 
coke and form a crust on top of the fire, need to be sliced 
quite often. 

Ques. 336. — Mention a few general maxims that are 
applicable to all boiler-rooms. 

Ans. — First, keep a clean fire; second, see that every 
square inch of grate surface is covered with a good live 
fire; third, keep as level a fire as possible; fourth, when 
cleaning the fire, be sure to clear all the clinkers and dead 
ashes away from the back end of the grates at the bridge- 
wall. 

Ques. 337. — Why should the face of the bridge-wall, 
especially, be kept clean and free from ashes and clinker? 

Ans. — For the reason that this is one of the best 
points in the furnace for securing good combustion, 
provided that the bridge-wall is kept clean from the grates 
up, and by keeping the back ends of the grates clean, the 
air is allowed a free passage through them and is per- 
mitted to come directly in contact with the hot fire-brick, 
and thus one of the greatest aids to good combustion is 
utilized. 

Ques. 338. — In firing bituminous coal, what is a good 
olan to pursue in regard to the fire-doors, with some 
iinds of boilers? 



BOILER OPERATION J31 

Ans. — ^They should be left slightly «^pen for a few 
seconds, immediately after throwing in a fresh fire. 

Ques. 339. — Give the reason for doing this. 

Ans. — Bituminous coal contains a large percentage of 
volatile (light or gaseous) matter, which flashes into 
flame the instant it comes in contact with the live fire in 
the furnace, and if a sufficient supply of oxygen is not 
present just at this particular time, the combustion will 
be imperfect, and the result will be the formation of 
carbon monoxide, or carbonic oxide gas, and the loss of 
about two-thirds of the heat units contained in the coal. 

Ques. 340. — How may this great loss of heat be 
guarded against, in a great measure? 

Ans. — By admitting a sufficient volume of air, either 
through the fire-doors, directly after putting in a fresh 
fire, or what is still better, providing air-ducts through 
the bridge-wall, or side walls, w^hich will bring the air 
in above the fire. 

Ques. 341. — What quantity of air is required for the 
complete combustion of 1 pound of coal? 

Ans. — By weight, 12 pounds; by volume, about 150 
cubic feet. 

Ques. 342. — Is there any advantage gained by heating 
this air before admitting it to the furnace? 

Ans. — There is a great advantage, provided the 
heat used for this purpose would otherw^ise be wasted. 
Great economy in fuel, and much better combustion, 
result from supplying heated air to the furnaces. 

Ques. 343. — Describe the Howden draught system, as 
used in the marine service. 



132 



QUESTIONS AND ANSWERS 



Ans. — There is a nest of tubes in the uptake that is 
enveloped by the hot gases on their way to the stack. 
The air is caused to pass through these tubes by a 




Fig. 90. Arrangement of the Howden Draught System, 



blower-fan, and as a consequence is heated to a high 
degree before passing into the ash-pit. Some of this hot 
air is also directed into the furnace above the fire, thus 
securine a sfood combustion of the fuel. 



BOILER OPERATION 



133 



Ques. 344. — What precautions should be taken regard- 
ing cleanliness of the tubes? 

Ans. — The tubes of all boilers shoula oe kept clean 
and free from soot, and especially does this apply to fire- 




FiG. 91. Air Heater o^ the Howden Draught System. 

tube boilers, for the reason that, when these tubes become 
clogged with soot, the efficiency of the draught is 
destroyed and the steaming capacity of the boiler is 
greatly reduced, because soot not only stops the draught 
but it is also a non-conductor of heat. 



134 QUESTIONS AND ANSWERS 

Ques. 345. — What methods are ordinarily employed 
for cleaning the soot and dust from tubes? 

Ans. — First, the steam jet, if properly made and 
connected by steam hose so as to get dry steam of high 
pressure, will do very effective v/ork; second, a scraper 
having steel blades expanded by springs so as to fit the 
inside of the tubes snugly, should be pushed through each 
tube once or twice during each twenty-four hours of 
service. This will cut the soot loose from the inside sur- 
face of the tubes, and greatly facilitate blowing it out 
with the steam jet. For the tubes of water-tube boilers 




Fig. 92. Scraper for Ci^Eaning Fire Tubes. 

the steam jet may be employed to advantage iu cleaning 
the outside surfaces, and a rotary scraper driven by a 
small steam turbine is used for cleaning the scale forma- 
tion from the inside. 

Ques. 346. — How often should a boiler be washed out 
and cleaned inside? 

Ans. — If the feed-water is impregnated to a consider- 
able extent with scale-forming matter, the boiler should 
be washed out every two weeks, and if the water is very 
bad, the time should be shortened to one week. 

Ques. 347. — How should a boiler be prepared for 
washing out? ^ 



BOILER OPERATION 135 

Ans.— The fire should be allowed to burn as low as 
possible, and then be all pulled out of the furnace, the 
fire-doors left slightly ajar, and the dampers left wide 
open in order that the boiler may gradually cool. 

Ques. 348. — Should a boiler be blown out, that is, 
emptied of water, while there is any steam-pressure in it? 

Ans. — It should not. 

Ques. 349.— Why not? 

Ans.— For the reason that the sudden change of 
temperature from hot to cold has an injurious eflfect on 
the seams and braces. It is as bad a practice to cool a 
boiler down too suddenly as it is to fire it up too quickly. 




Fig. 93. Turbine Cleaner for Water Tubes. 

Ques. 350. — What effect does the too sudden contrac- 
tion or expansion of the boiler-plates have upon the 
riveted seams? 

Ans. — Leaks are created, and very often small cracks 
radiating from the rivet-holes are started, and these 
becoming larger with each change of temperature, will 
finally destroy the strength of the seam and serious 
results will follow. 

Ques. 351. — Suppose that all of the fire has been 
pulled from the furnace and that the boiler has stood 
until the steam-gauge indicates 20 pounds pr^.ssure. 



136 QUESTIONS AND ANSWERS 

would it then be safe to b] j';^ ^^.1 of the water out of the 
boiler? 

Ans.— It would not, for the reason that the tempera- 
ture of steam at 20 pounds pressure is 260 degrees 
Fahrenheit, and it may be assumed that the temperature 
of the metal of the boiler is at or near this temperature 
also. Assuming the temperature of the atmosphere in 
the boiler-room to be 60 degrees Fahrenheit there will be a 
range of 260 degrees — 60 degrees = 200 degrees Fahren- 
heit temperature for the boiler to pass through within a 
short time, which will certainly have a bad effect, and 
besides this, the boiler shell will be so hot that the loose 
mud and sediment left after the water has run out is 
liable to become baked upon the bottom sheets, making 
it much harder to remove. 

Ques. c52. — Under what conditions is it best to empty 
a boiler of water preparatory to washing it out? 

Ans. — After the boiler has become comparatively cool 
and there is no pressure indicated by the steam-gauge, 
the blow-off cock may be opened and the water allowed 
to run out. The gauge-cocks and drip-valve to the 
water-column should be left open to allow the air to enter 
and displace the water, otherwise there will be a partial 
vacuum formed in the boiler, and the water will not run 
out freely. 

Ques. 353. — Mention some of the important duties of 
the boiler-washer. 

Ans. — After the water has all run out and the boiler 
has cooled sufficiently to permit it, he should go inside 
(provided there is a man-hole) and after having thorou^'hly 



BOILER OPERATION 13? 

cleaned the inside of the boiler, he should closely examine 
all of the braces and stays, and if any are found loose or 
broken, they should be repaired at once, before the boiler 
is put in service again. The soundness of braces, rivets, 
etc., can be ascertained by tapping them with a light 
hammer. 

Ques. 354. — What should be done with the tubes of 
fire-tube boilers when they become coated with scale on 
their outside surfaces? 

Ans. — The boiler should be taken out of service, laid 
up temporarily, and the tubes taken out, cleaned, and 
those that are not corroded or pitted too badly may be 
made almost as good as new by cutting off 8 or 10 inches 
of the ends and welding pieces of new tubing on, to bring 
the tubes back to their original length, after which they 
may be put back in the boiler and be good for a long term 
of service. While the tubes are out of the boiler for re- 
pairs the boiler-washer will have a good opportunity to get 
inside and clean and inspect every portion of the inside. 

Ques. 355. — What precautions should be taken when 
connecting a recently fired-up boiler with the steam main 
or header? 

Ans. — First, the steam in the boiler to be connected 
should be raised to the same pressure as that in the main, 
then the dampers should be closed and the steam stop- 
yalve should be opened slightly, just enough to permit a 
^mall jet of steam to pass through, which can be heard 
by placing the ear near the body of the valve. This jet 
of steam may be passing from the main into the newly 
connected boiler, or vice versa. Whichever way it is 




Fig. 94. Squake Open Heater. 



BOILER OPERATION 



139 



going, the valve ought not to be opened any farther until 
the flow of steam stops. This will indicate that the pres- 
sure has been equalized be- 
tween the boiler and the main, 
and it will then be found that 
the valve will move much 
easier, and it may be gradually 
opened until it is wide open. 

Ques. 356.— Should cold 
feed-water ever be pumped 
into a boiler that is under 
steam? 

Ans.— It should not, if it is 
possible to prevent it. 

Ques. 357. — How may the 
feed-water be heated econo- 
mically? 

Ans. — By passing it 
through a feed-heater in which 
the heating agent employed is 
the exhaust steam from the 
engines. 

Ques. 358. — How should the feed-water be supplied 
to a boiler while the boiler is being fired? 

Ans. — It should be supplied just as fast as it is evap- 
orated. The firing can then be even and regular. 

Ques. 359. — If the supply of feed-water should sud- 
denly be cut off owing to breakage of the pump or some 
other cause, and no other source of supply was available, 
what should be done? 




Fig. 95. Interior View oP 
Open Heater. 



140 



QUESTIONS AND ANSWERS 



Ans. — The dampers should be closed immediately, and 
all of the draught stopped. The fires should be deadened 
by shoveling wet or damp ashes in on top of them, or if 
ashes can not readily be procured, bank the fires over with 

green coal broken into fine 
bits. This, with the draught 
all shut off, will keep the fires 
dead, and if repairs to the 
feed-supply can not be made 
within a short time, the fires 
should be pulled, that is, if 
they have become deadened 
sufficiently. 

Ques. 360.— Should the 
fires be pulled while they are 
burning lively? 

Ans. — No; because the 
stirring will only serve to 
increase the heat, and the dan- 
ger will be aggravated. 

Ques. 361.— What is the 
primary object of making 
evaporation tests of boilers? 

Ans. — To ascertain how 
many pounds of v/ater per 
pound of coal the boiler is evaporating. 

Ques. 362. — What other important details relating 
io the operation of the boilers may be ascertained through 
a well-conducted evaporation test? 

Ans. — First, the efficiency of the boiler and furnace as 




f'iG. 96. Baragwanath Steam 
Jacket Feed Water Heater. 



BOILER OPERATION 



141 



an apparatus for the consumpticn ^f fuel and the evap- 
oration of water; second, the relative value of different 
varieties of coal, and 
other fuels, as heat- 
producers; third, 
whether the boilers, as 
they are operated un- 
der ordinary every- 
day conditions, are 
being operated as 
economically as they 
should be; fourth, in 
case the boilers, owing 
to an increased de- 
mand for steam, fail 
to supply a sufficient 
quantity, whether or 
not additional boilers 
are needed, or whether 
the trouble could be 
overcome by a change 
of conditions in the op- 
eration of the boilers. 

Ques. 363.— What 
are the principal data 
to be noted down dur- 
ing the progress of an 
evaporation test? 

Ans. — First, time — the number of hours that the test 
is conducted: second, the kind of coal burned; third. 




Fig 97. Ci^osed Feed Water Heater. 



142 QUESTIONS AND ANSWERS 

weight of coal consumed; fourth, weight of water evap- 
orated during the test; fifth, weight of dry ash returned; 
sixth, moisture in the coal, per cent, seventh, dry coal 
corrected for moisture* eighth, weight of combustible; 
ninth, moisture in the steam, per cent: tenth, water 
corrected for moisture in the steam, eleventh, average 
temperature of the feed- water; twelfth, average tempera- 
ture of the escaping gases; thirteenth, square feet of 
grate surface; fourteenth, square feet of heating sur- 
face; fifteenth, ratio of grate surface to heating surface. 

Ques. 364. — How may the weight of the coal consumed 
during the test be ascertained? 

Ans.— By havmg a small platform scales fitted with 
a wooden platform large enough to accommodate a wheel- 
barrow, or, in lieu of a barrow, a box large enough to 
contain two or three hundred pounds of coal. Each 
wheel-barrow load, or boxful of coal that goes to the 
boiler undei test can then be v/eighed and the figures be 
placed upon a tally-sheet and added together at the close 
of the test, thus giving the total weight of coal consumed 
during the test. If, at the close of the test, there is any 
of the weighed coal left on the floor, it should be weighed 
back and deducted from the total weight. 

Ques. 365. — How may the weight of water evaporated 
during the test be ascertained? 

Ans. — By having a hot-water meter fitted in the branch 
feed-pipe leading to the boiler under test, or if this is not 
to be had, a substitute equally as accurate can be made 
by placing two small water-tanks, each having a capacity 
of 8 or IQ cubic feet, in the vicinity of the feed-pump. 



BOILER OPERATION 



143 



These tanks can be made of light tank-iron, and each 
should be fitted with a nipple and valve, near the bottom, 
for connection with the suction side of the feed-pump. 
The tops of the tanks may be left open. A pipe leading 
from the main water-supply, with a branch to each tank, 
is also needed for filling them. If an open feed-water 
heater is used, and it is possible to place the tanks low 
enough to allow a portion of the hot water from the 




TOF^PPUM P 



heater to be led into them by gravity, it will be desirable 
to do so. If this can not be done, some other provision 
should be made for at least partially warming the water 
before it goes to the boiler. The exact capacity of each 
one of these two tanks, either in cubic feet or in pounds 
of water, should be ascertained, and then all of the feed- 
water that is supplied to the boiler during the test is to be 
first passed through the tanks, which should be numbered 



144 



QUESTIONS AND ANSWERS 



one and two respectively, in order to prevent confusion in 
keeping a record of the number of tankf uls of water used 
during the test. Two tanks should be provided, in order 
that while the feed-pump is drawing the water from one, 
the other one may be filled. The feed-pump that is used 
to supply the boiler under test should have no connection 
whatever with the main feed-supply. By keeping tab of 
the number of tankfuls of water used during the test, and 

TABLE 6 

WEIGHT OF WATER AT VARIOUS TEMPERATURES 



Temper- 


Weight per 


Temper- 


Weight per 


Temper- 


Weight per 


ature 


Cubic Foot 


ature 


Cubic Foot 


ature 


Cubic Foot 


32° F. 


62.42 lbs. 


132° F. 


61.52 lbs. 


230° F. 


59.37 lbs. 


42° 


62.42 


142° 


61.34 


240° 


59.10 


52° 


62.40 


152" 


61.14 


250° 


58.85 


62° 


62.36 


162' 


60.94 


260° 


58.52 


72° 


62.30 


172' 


60.73 


270° 


58.21 


82° 


62.21 


182^ 


60.50 


300° 


57.26 


92° 


62.11 


IQ2° 


60.27 


330° 


56.24 


102° 


62.00 


202° 


60.02 


360° 


55.16 


112° 


61.86 


212'' 


59.76 


390° 


54.03 


122'' 


61.70 


220° 


59.64 


420° 


52.86 



multiplying this by the capacity of each tank, the total 
weight of water evaporated is ascertained. 

Ques. 366. — How is the weight of dry ash ascertained? 

Ans. — No water should be allowed to come in contact 
with the ashes during the test, or if it is absolutely neces- 
sary to use water, it should be used as sparingly as 
possible, and as the ashes are pulled from the furnace or 
ash-pit, they should be thrown to one side, and allowed to 
become dry, after which the weight can be ascertained by 
means of the scales that was used for weighing the coal. 



BOILER OPERATION 145 

Ques. 367. — How is the amount of moisture in the 
coal ascertained? 

Ans. — This can generally be obtained from the reports 
of the geologist of the state in which the coal was mined. 

Ques. 368. — How is the weight of dry coa! corrected 
for moisture ascertained? 

Ans. — Deduct the percentage of moisture in the coal 
from the total weight of coal consumed. 

Ques. 369. — How is the weight of combustible ascer- 
tained? 

Ans. — Deduct the weight of dry ash returned from the 
weight of dry coal corrected for moist^ire. 

Ques. 370. — How is the percentage of moisture in the 
steam determined? 

Ans. — By means of an instrument called a calorimeter, 
or if such an instrument is not at hand, the condition of 
the steam as regards its dryness may be approximately 
estimated by observing its appearance as it issues from a 
pet-cock, or other small opening into the atmosphere. 
Dry, or nearly dry steam, containing about 1 per cent of 
moisture, will be transparent close to the orifice through 
which it issues, and if it is of a grayish white color it may 
be estimated to contain not over 2 per cent of moisture. 

Ques. 371. — How is water corrected for moisture in 
the steam arrived at? 

Ans. — Deduct the percentage of moisture in the steam 
from the total weight of water evaporated during the 
test. 

Ques. 372. — How is the average temperature of the 
feed-water obtained? 



146 



QUESTIONS AND ANSWERS 



Ans. — By means of a hot-water thermometer connected 
to the feed-pipe near to the check-valve, but between it 
and the feed-pump. If the thermometer is not attached 
to the feed-pipe, the temperature of 
the water in each tank should be 
taken and noted down, during the time 
that the feed-pump is drawing from it. 
From these notations, made at regular 
intervals during the progress of the 
test, the average temperature of the 
feed-water is easily calculated. 

Ques. 373. — How is the average 
temperature of the escaping gases 
determined? 

Ans. — By readings taken at regular 
intervals from a thermometer con- 
nected in the uptake. 

Ques. 374. — What should be done 
with the boiler and furnace before be- 
ginning an evaporative test? 

Ans. — The boiler should be thor- 
oughly cleaned, both inside and out- 
side, and especially the heating sur- 
face, by scraping and blowing the soot 
out of the tubes, if it be a return-tu- 
bular boiler, and blowing the soot and 
ashes from between the tubes if it is a 
water-tube boiler. All dust, soot, and 
ashes should be removed from the out- 
side of the shell, and also from the ^^hermom'eterJ^" 



BOILER OPERATION 147 

combustion chamber and smoke connections. The grate- 
bars and sides of the furnace should be cleared of all 
clinker, and all air-leaks made as tight as possible. 

Ques. 375. — What should be done with the water- 
connections? 

Ans. — The boiler and all of its water-connections 
should be perfectly free from leaks, especially the blow* 
off valve or cock. If any doubt exists as to the latter, it 
should be plugged, or a blind flange put on it. 

Ques. 376. — Why is it required that especial care be 
exercised regarding the water-connections? 

Ans. — For the reason that the test is made for the pur- 
pose of ascertaining the exact quantity of water that the 
Wler will evaporate with a given weight and kind of coaU 
md if any of the water fed to the boiler during the test is 
allowed to leak away, or if any water, other than that 
which has been measured by passing it through the tanks, 
is allowed to get into the boiler during the test, the results 
will be misleading and unreliable. 

Ques. 377. — Before starting the test, what other details 
regarding the boiler should be attended to carefully? 

Ans. — The boiler should be thoroughly heated, by 
having been run for several hours at the ordinary rate. 
The fire should then be cleaned and put in good condition 
to receive the fresh coal that has been weighed for the test. 

Ques. 378. — What should be done regarding the 
water-level? 

Ans. — At the time of beginning the test, the water- 
level in the boiler should be at or near the height ordi- 
narily carried, and its position should be marked by tying. 



148 QUESTIONS AND ANSWERS 

a cord around one of the guard-rods of the gauge-glass, 
and, to prevent any possibility of error, the height of the 
water in the glass should be measured in inches, and a 
memorandum made of it. 

Ques. 379. — What data regarding the steam-pressure 
should be recorded? 

Ans. — The steam-pressure as indicated by the gauge 
should be noted at the time of starting the test, and also 
at regular intervals during the progress of the test, in 
order that the average pressure may be obtained. 

Ques. 380. — When should the test begin? 

Ans. — When all of the conditions just described have 
been complied with and the first lot of weighed coal has 
been fed to the furnace and the feed-pump is receiving 
water from one of the measuring tanks, the time should 
be noted and recorded as the starting time. 

Ques. 381. — What length of time should an evapora- 
tion-test be conducted? 

Ans. — Ten hours, if it is possible to continue it Ihat 
long. 

Ques. 382. — What conditions regarding the steam- 
pressure, condition of the fire and the water-level should 
prevail at the close of the test? 

Ans. — They should be as nearly as possible the same 
at the close as they were at the beginning. The water- 
level should be the same and the quantity and the condition 
of the fire, also the steam pressure. 

Ques. 383.— How may this be accomplished? 

Ans. — Only by very careful work toward the close of 
the test. 



BOILER OPERATION 149 

Ques. 384. — If any of the weighed coal is left on the 
floor at the close of the test, what should be done with it? 

Ans. — It should be weighed back and its weight 
deducted from the total weight. 

Ques. 385. — If a portion of water is left in the last 
tank tallied, what disposition should be made of it? 

Ans. — It should be measured and deducted from the 
total. 

Ques. 386. — In making a test of the efficiency of the 
boiler, what is one of the most essential conditions to be 
taken into consideration? 

Ans. — The boiler should be operated at its fullest 
capacity, from the beginning to the end of the test, and 
arrangements should be made to dispose of the steam as 
fast as it is generated. 

Ques. 387. — How may this be done? 

Ans. — If the boiler is in a battery and connected to 2i 
common header, the other boilers can be fired lighter dur* 
ing the test; but if there is but the one boiler in use, a 
waste-steam pipe should be temporarily connected, 
through which the surplus steam, if there is any, can be 
discharged into the open air, through a valve regulated 
as required. 

Ques. 388. — If the boiler under test is fed by an 
injector instead of a pump during the test, from whence 
should the steam-supply for the injector be taken? 

Ans. — The steam for the injector should be taken 
directly from the boiler under test, through a well- 
protected pipe. The steam for the pump, if one is used, 
should also be taken from the same source. 



150 QUESTIONS AND ANSWERS 

Ques. 389. — How should the temperature of the feed- 
water be taken when an injector is used? 

Ans. — It should be taken from the measuring tanks, 
or at least from the suction side of the injector. 

Ques. 390.— Why? 

Ans, — Because the water in passing through the 
injector receives a large quantity of heat imparted to it 
by live steam directly from the boiler, and the tempera- 
ture of the water after it leaves the injector would not be 
a true factor for use in calculating the results of the 
test. 

Ques. 391. — For obtaining reliable and economical 
results in an evaporation-test, what conditions are 
essential regarding the draught? 

Ans. — There should be a good, strong draught, which 
can be regulated by a damper, as desired. There should 
also be a draught-gauge connected to the uptake, for the 
purpose of measuring the draught, 

Ques. 392. — Why is it necessary to measure the 
draught? 

Ans. — The principal reason for measuring the draught 
is that in making comparative tests of the heating value 
of different varieties of coal, the conditions should be the 
same as near as possible in all of the tests made, and 
especially should this be the case with the draught. 
Therefore, by using a draught-gauge and measuring the 
draught during each test, there will be no uncertainty 
regarding this very important element. 

Ques. 393. — Describe the construction and operation 
of a draught-erauge. 



iiOILER OPERATION 



151 




Ans. — ^The usual form of drr^^^ht-gauge is a glass 
tube bent in the shape of the letter U. One leg is con- 
nected to the uptake by a tmM rubber hose, while the 
other leg is open to the atmosphere. 

A scale marked in tenths of an inch is fitted between 
the two legs of the gauge. The 
glass tube is partly filled with water, 
which will, when there is no draught, 
stand at the same height in both 
legs, provided the instrument stands 
perpendicular, which is its normal 
position. When connected to the 
uptake, the suction caused by the 
draught will cause the water in the 
leg to which the hose is attached to 
rise, while the level of the water in 
the leg that is open to the atmos- 
phere will be equally depressed, and 
the extent of the variation in frac- 
tions of an inch is the measure of 
the draught. Thus the draught is 
referred to as being .5 .7 or .75 inch. 

Ques. 394. — What is the least 
draught that should be used, in or- 
der to obtain good results? 

Ans. — The draught should not be less than .5 inch. 
Better results may be obtained with a draught of .7 inch. 

Ques. 395. — If the test is made for the purpose of 
determining the efficiency of the boiler and setting as a 
whole, including grate, draught, etc., and also for compar* 




Fig. 100. Draught Gauge. 



152 QUESTIONS AND ANSWERS 

ing the heating qualities of diflferent kinds of coal, what 
must the result be based upon? 

Ans. — Upon the number of pounds of water evapo- 
rated per pound of coal burned. 

Ques. 396. — What is implied in the expression "per 
pound of coal burned" as used in this connection? 

Ans. — It includes not only the purely combustible 
matter in the coal, but the non-combustible also, such as 
ash, moisture, etc. Some varieties of Western coal con- 
tain as high as 12 to 14 per cent of moisture, and the 
ability of the furnace to extract heat from the mass is to 
be tested, as well as the ability of the boiler to absorb and 
transmit that heat to the water. 

Ques. 397. — If the test is to determine the efficiency 
of the boiler itself as an absorber and transmitter of heat, 
what must be the factor for working out the result? 

Ans. — The weight of the combustible alone must be 
considered. 

Ques. 398. — When making a series of tests for the 
purpose of comparing the economical value of dififerent 
kinds of coal, what conditions should prevail? 

Ans. — The conditions should be as nearly uniform as 
possible; that is, let the tests all be made under ordinary 
working conditions, and with the same boiler or boilers, 
and if possible with the same fireman. 

Ques. 399. — What is meant by the term '^equivalent 
evaporation," as applied to the results of an evaporation- 
test? 

Ans. — The term ^'equivalent evaporation,*' or t ^e 
evaporation from and at 212 degrees, assumes that the 



BOILER OPERATION 153 

feed-water enters the boiler at a temperature of 212 
degrees and is evaporated into steam at 212 degrees tem- 
perature, and at atmospheric pressure, as, for instance, 
if the top man-hole plate were left out, or some other 
large opening in the steam-space of the boiler allowed the 
steam to escape into the atmosphere as fast as it was 
generated. 

Ques. 400. — Why is it necessary to introduce this 
feature into calculations of the results of evaporation- 
tests? 

Ans. — Owing to the variation in the average tem- 
perature of the feed-water used in different tests, and also 
the variation in the average steam-pressure, it is 
absolutely necessary that the results of all tests be 
brought by computation to the common basis of 
212 degrees in order to obtain a fair and just comparison. 

Ques. 401. — Describe the method of calculation by 
which this is done. 

Ans. — Suppose an evaporation-test to have been made, 
and that the average steam-pressure by the gauge was 
85 pounds, which equals 100 pounds absolute pressure, 
and that the average temperature of the feed-water was 
141 degrees. By reference to Table 1, Chapter 1, it will 
be found that in a pound (weight) of steam at 100 pounds 
absolute pressure there are 1,181.1 heat units or thermal 
units, and in a pound of water at 141 degrees temperature 
there are 109.9 heat units. It therefore required 
1,181.1 — 109.9 = 1,071.9 heat units to convert 1 pound 
of feed-water at 141 degrees temperature into steam at 
85 pounds gauge, or 100 pounds absolute pressure. Now 



154 QUESTIONS AND ANSWERS 

to convert a pound of water at 212 degrees temperature 
into steam at atmospheric pressure and 212 degrees tem- 
perature, requires (according to Table l) 965.7 heat units, 
and the 1,071.9 heat units would evaporate 1,071.9 -f- 965.7 
= 1.11 pounds of water from and at 212 degrees. The 
1.11 is the factor of evaporation for 85 pounds gauge 
pressure, and 141 degrees temperature of feed-water. 

Ques. 402. — What use is made of this factor of evap- 
oration in the calculation? 

Ans. — One of the results of the test was * 'weight of 
water corrected for moisture in the steam,*' and by mul- 
tiplying this result by the factor of evaporation, the 
''equivalent evaporation'' is ascertained. 

Ques. 403. — Upon what is the factor of evaporation 
based, in any test? 

Ans. — Upon the steam-pressure and the temperature 
of the feed-water. 

Ques. 404. — Give the formula for finding this factor 
for any test. 

TT L^ 

Ans. — The formula is: Factor =— -—r, in which H== 

yo5.7 

total heat in the steam, h = total heat in the feed-water, 
and 965.7 = the number of heat units in a pound of 
steam at atmospheric pressure and 212 degrees tempera- 
ture. Table 7 gives the factor of evaporation, already 
calculated, for various pressures and temperatures. 

Ques. 405. — If it is desired to ascertain the cost of 
coal for generating the steam used for operating an engine 
that uses 30 pounds of steam per horse-power per hour, 
what is the method of calculation? 



BOILER OPERATION 



155 



Ans. — If the engine uses 30 pounds of steam per horse- 
power per hour, and it has been found by the test that 
1 pound of the coal used would evaporate 9 pounds of 
water into steam of the pressure at which it is supplied to 
the engine, the actual consumption of fuel by the engine 

Table / 
Factors of Evaporation 



si 


1° 


CO 

Si 

|3 


|1 


05 




CO 


CO 

r.l 

;3 M 


en 

=3 M 


en 

Si 








<2 w 




rt en* 


^ 

p-l 


r*\ en 
^ en 


C^ en 

D 

Oh 


/h CO 


212° 


1.027 


1.030 


1.032 


1.035 


1.037 


1.039 


1. 041 


1.043 


1.047 


200° 


1.039 


1.042 


1045 


1.047 


1.050 


1.052 


1.054 


1.056 


1.059 


igi" 


1.049 


1.052 


1.054 


1.057 


1.059 


1. 061 


1.063 


1.065 


1.069 


182° 


1.058 


1. 061 


1.064 


1.066 


1.069 


1. 071 


1.073 


1.075 


1.078 


173° 


1.067 


1.070 


1.073 


1.076 


1.078 


1.080 


1.082 


1.084 


1.087 


164° 


1.077 


1.080 


1.083 


1.085 


1.087 


1.090 


1. 091 


1.093 


1.097 


152° 


1.089 


1.092 


1.095 


1.098 


1. 100 


1. 102 


I. 104 


I. 106 


1. 109 


143° 


1.099 


1. 102 


1. 105 


1. 107 


I. 109 


I.III 


1. 113 


I.II5 


1. 119 


134° 


1. 108 


i.iii 


1. 114 


1. 116 


I. 119 


1. 121 


I.I23 


I.I25 


1. 128 


125° 


1. 118 


1. 121 


1. 123 


1.126 


I.I28 


1. 130 


1. 132 


1. 134 


1. 137 


113° 


1. 1 30 


1. 133 


1. 136 


1. 138 


1. 140 


I- 143 


I. 145 


1. 146 


1. 150 


104° 


1.138 


1. 142 


1. 145 


1. 148 


1. 150 


1. 152 


I. 154 


1.15^ 


1. 159 


95! 


I.I4Q 


1. 152 


1. 154 


1. 157 


I. 159 


1. 161 


I. 163 


1. 165 


1. 169 


86' 


I.158 


1. 161 


1. 164 


1. 166 


1. 169 


1. 171 


I.I73 


I.I74 


1. 178 


77° 


1. 167 


1. 170 


1. 1 73 


1. 176 


I. 178 


I. 180 


I.IS2 


1. 184 


I.I87 


65° 


1. 180 


1. 183 


1. 186 


1. 188 


I. T9O 


1. 192 


I. 194 


I. 196 


1.200 


56° 


1. 189 


1. 192 


1. 195 


1. 197 


1.200 


1.202 


1.204 


1.206 


1.209 


47° 


1. 199 


1. 201 


1.204 


1.207 


1.209 


I. 211 


I. 213 


I. 215 


1. 2X8 


38° 


1.208 


1. 211 


1. 214 


1. 216 


I.21S 


1.220 


1.222 


1.224 


1.228 



would be as follows: 30 -^ 9 = 3.33 pounds of coal per 
horse-power per hour, which, multiplied by the total horse- 
power developed by the engine, will give the total weight 
of coal consumed in one hour's run. 

Ques. 406. — What is the meaning of the expression 
* 'boiler horse-power?" 



156 QUESTIONS AND ANSWERS 

Ans. — The latest decision of the American Society of 
Mechanical Engineers regarding Lie horse-power of 
a boiler is *'that the unit of commercial horse-power de- 
veloped by a boiler shall be taken as 34J^2 units of evapor- 
ation." That is, 34>^ pounds of water evaporated per 
hour from a feed temperature of 212 degrees into steam 
of the same temperature. 

This standard is equivalent to 33.317 heat units per 
hour. It is also practically equivalent to an evaporation 
of 30 pounds of water from a feed temperature of 
100 degrees Fahrenheit into steam of 70 pounds gauge- 
pressure. 

Ques. 407. — According to this rule, what would be \ 
the horse-power of a boiler in which during a 10-hour 
test, the evaporation from and at 212 degrees was found 
by calculation to have been 86,250 pounds of water? 

Ans. — The horse-power developed would be 86,250 -^ 
10-^ 34.5 = 250 horse-power. 

Ques. 408. — In what way can the maximum economy 
in the consumption of coal be obtained? 

Ans. — There is only one way, and that is by keeping 
a continuous supply of coal on the fires and admitting a 
regular and sufficient quantit^^ of air for its combustion. 

Ques. 409. — Can these conditions be reached by hand 
firing? 

Ans. — They can not, no matter how careful and skil- 
ful the firemen may be. 

Ques. 410. — Mention two of the principal disadvan- 
tages attending hand firing. 

Ans. — First, durin the time of firing the furnace 



BOILER OPERATION 157 

door is wide open, thus admitting a large volume of cold 
air ; second, immediately after throwing in a fresh supply 
of coal, there is a sudden generation of gas, a large per- 
centage of which escapes without being entirely consumed, 
and much heat is thus wasted. 

Ques. 411. — What are the principles governing the 
operation of mechanical or automatic stokers? 

Ans. — First, a continuous supply of coal and air; 
second, thorough regulation of the supply of fuel and air, 
according to the demand upon the boilers for steam; 
third, the intermittent opening and closing of the furnace 
doors is entirely prevented. 

Ques. 412. — What are some of the disadvantages 
attending the use of mechanical stokers? 

Ans. — First, the great cost of installing them; second, 
in case of a sudden demand upon the boilers for more 
steam, the mechanical stoker can not respond as promptly 
as in hand firing; third, the extra cost for power to 
operate them. 

Ques. 413. — How many different classes of mechanical 
stokers are in use? 

Ans. — Four general classes. 

Ques. 414. — Describe the construction and operation 
of stokers belonging to Class 1. 

Ans. — The grate consists of an endless chain of short 
bars, that travels in a horizontal direction from the front 
to the back of the furnace, over sprocket wheels operated 
either by a small auxiliary engine or by power derived 
from an overhead line of shafting in front of the boilers. 
The motion of the endless chain of grates is of course very 



158 



QUESTIONS AND ANSWERS 









• i; / ife? 



^..^^ 



BOILER OPERATION 



159 



slow, but it is continuous and regular, receiving the supply 
of coal at the front and depositing the ashes at the bacK 
end, where they drop into the ash-pit. 







o o 



OS 

OS 

O 






Ques. 415. — What type of stokers is included in 
Class 2 ? 

Ans. — Stokers having grate-bars somewhat after the 
ordinary hand-fired type, but having a continuou*? raotioa 



160 



QUESTIONS AND ANSWERS 



uo and down, or forward and back. Although this 
motion is slight, it serves to keep the fuel stirred and 
loosened, thus preventing the fire from becoming sluggish 
Ques. 416.— What position do the grate-bars in 
(■".lass 2 occupy? 




Fig. 103. ViCAES Mechanical Stoker. 

^:Vns.— Either horizontal, or slightly inclined, and their 
constant motion tends to gradually advance the coal from 
the front to the back end of the furnace. 

Ques. 417.— What kinds of stokers are included in 

Class 3 ? 

Ans.— Stokers in which the grates are steeply inclined. 



BOILER OPERATION 



161 



The coal is fed onto the upper ends of the gates, which, 
having a slow motion, gradually force the coal forward as 
fast as required. In some stokers of this class, as, for 
instance, the Murphy, the grates incline from the sides 
towards the middle of the furnace, but in the majority of 
cases the inclination is from the front towards the back. 




Fig. 104. The Murphy Automatic Furnace. 

Ques. 418. — What is the leading feature governing the 
operation of stokers belonging to Class 4 ? 

Ans. — The coal is supplied from underneath the grates, 
and is pushed up through an opening left for the purpose 
midway of the length of the furnace. The gases, on 
being distilled, come in contact immediately with the hot 
bed of coke on top^ and the result is good combustion. 

Ques. 419. — What are stokers belonging to Class 4 
called? 



162 



QUESTIONS AND ANSWERS 



Ans. — Under-feed stokers. 

Ques. 420. — What methods are emplcyed for forcing 
the coal up into the furnace with under-feed stokers? 




Ans. — Steam is the active agent, either by means of 
a steam-ram, or a long, slowly revolving screw, driven 
by a small engine- 



BOILER OPERATION 



183 



Ques. 421. — How is the air supplied when an under- 
feed stoker is used? 







C ^ G 



"^ TO 



w?i; 



to 



__ > 1) c^ 

o o :=!^:> 



Ans. — Forced draught is employed, and the air is 
blown into the furnace through tuyeres. 

Ques. 422. — How is the coal supplied to mechanical 
stokers, other than the under-feed type? 

Ans. — In two ways; either by being shoveled by hand 



164 QUESTIONS AND ANSWERS 

into hoppers in front of and above the grates, or, as is the 
case in most of the large plants using them, it is elevated 
by machinery and deposited in chutes, through which it 
is fed to each boiler by gravity. The coal used in 
mechanical stokers is in the form of screenings or nut 
coal. 

Ques. 423. — Have mechanical stokers for feeding coal 
been applied in the marine service to any great extent? 

Ans. — They have not, up to the present time. 




'^ 



Fig. 107. Jones Under-feed bxoKER, Having a Steam Ram. 

Ques. 424. — In what way is it possible to successfully 
use automatic or mechanical stokers on marine boilers? 

Ans. — By the use of liquid fuels, such as petroleum, 
blast-furnace oil, tar oil, etc. 

Ques. 425. — Of what does petroleum consist? 

Ans. — Petroleum consists practically of carbon, 
hydrogen, and oxygen, in the following proportions: 
Carbon, 85 per cent; h3drogen, 13 per cent, and oxygen, 
2 per cent. 

Ques. 426. — What is the heating value of 1 pound of 
petroleum? 



BOILER OPERATION 166 

Ans. — About 20,000 heat units, or about one-third 
more than the best coal. 

Ques. 427. — How is petroleum fed to the furnaces? 

Ans. — By being forced through nozzles having two 
or three holes, or annular spaces, from one of which th^ 
petroleum flows out, under pressure, while a jet of stearr 
or compressed air issuing from another orifice catch^ 
the oil and ''pulverizes" it into a fine spray, in which 
form it strikes the fire. The air for combustion is 
admitted through a third orifice, or if not thus supplied. 




Fig. 108. Sectionai, View of Jones Under-eeed Stoker. 

the air for combustion is admitted by suitable orifices in 
the furnace front. 

Ques. 428. — How is the furnace arranged for burning 
petroleum? 

Ans. — A layer of broken fire-brick or asbestos is 
placed on the grate, and fire-brick screens, or bafflers, 
are placed in the way of the flame, thus providing a red- 
hot surface against which it impinges. Otherwise the 
combustion would be greatly hindered by the compara- 
tively cool surfaces of the boiler-plates and tubes. 

Oues. 429- — What agent has been found to be the best 



166 



QUESTIONS AND ANSWERS 



for pulverizing the petroleum and spraying it into the 
furnace? 

Ans. — Compressed air, slightly heated. 

Ques. 430 — What is one of the disadvantages attend- 
ing the use of steam for this purpose? 

i\ns. — The danger of the flame being extinguished by 
water that is sometimes carried over with the steam. 




smmii£Bifi£B 



Fig. 109. Petroi.eum Burner eor Boiler Furnace. 

Ques. 431. — How is the oil supplied to the nozzles? 

Ans. — By means of pumps that draw it from the 
bunkers and discharge it into a reservoir, and from 
thence it is fed to the burners. 

Ques. 432. — What are the advantages in favor of 
petroleum fuel, especially for the marine service? 

Ans. — First, superior evaporation, and, as a conse- 
quence, great reduction in the weight of fuel to be carried; 



BOILER OPERATION 167 

Second, less space occupied by the fuel and ease of ship- 
pfig it into the bunkers; third, reduction of stoke-hold 
fofce, also less space required in the stoke-hold; fourth, 
reg^ularity of combustion and no reduction of power, due 
to cleaning fires, they being always clean and in a good 
condition; fifth, increased durability of boilers, owing to 
the fact that there are no variations of temperature, due 
to opening fire-doors, for coaling or cleaning; sixth, 
greater control over the expenditure of fuel, consequently 
less waste of steam at the safety valves, also less danger 
of a short supply of steam in case of a sudden demand 
upon the boilers. 

Ques. 433. — What are some of the principal objections 
to its use on board of vessels? 

Ans. — First, limited supply; second, vessels proceed- 
ing on long voyages could not, with present facilities, 
replenish their bunkers when required; third, danger of 
the generation of inflammable gases; fourth in war-ships 
the risk of possible loss of the fuel, in the event of injury 
to the bunker containing it. 

Ques. 434. — Has the combination of coal and petro- 
leum., in the same furnace, ever been attempted? 

Ans. — Experiments along this line are being made in 
the British and other navies. 

Ques. 435. — How are the furnaces fitted for this 
purpose? 

Ans. — The same as for hand firing with coal, and in 
addition, a number of nozzles are placed in the front 
above the fire for injecting the petroleum over the incan- 
descent coal. 



168 QUESTIONS AND ANSWERS 

Ques. 436. — Upon what does the efficiency of a steam- 
ship, or of a manufacturing establishment in which steam 
is used for power, largely depend? 

Ans. — Upon the condition of the boilers and the care 
and labor expended for their preservation. 

Ques. 437. — What was formerly one of the most dan- 
gerous and active agents in the deterioration of boilers, 
especially in the marine service? 

Ans. — Corrosion of the boiler-plates and stays. 

Ques. 438. — What was found, by a long series of 
experiments, to be the principal cause of this corro- 
sion? 

Ans. — The action of the fatty acids evolved by 
saponification from the heated tallow and vegetable oils, 
used at the time for the internal lubrication of the cylin- 
ders and valve-chests. 

Ques. 439. — How were these oils carried into the 
boilers? 

Ans. — In condensing systems, where the water of con- 
densation was used for feed-water, the waste oil in the 
exhaust steam mingled with the feed-water and was 
carried into the boilers. 

Ques. 440. — How has the danger from this source been 
largely obviated in late years? 

Ans. — By the use of mineral oils for internal 
lubrication. 

Ques. 441. — In what other way has the danger of 
corrosion been lessened? 

Ans. — By the use of mild steel instead of iron plates 
in the construction of boilers. This steel is made by the 



BOILER OPERATION 169 

Seimens-Martin process, and is much stronger than iron 
and less liable to corrosive action. 

Ques. 442. — Of what material are marine boilers now 
made entirely? 

Ans. — ^Of steel, except the tubes, which are usually 
made of iron in the mercantile service. Steel tubes are 
used in war-ships. The furnaces and internal parts, that 
have to be welded or flanged, are made from specially 
soft steel plates. 

Ques. 443. — What is the principal cause of corrosion 
in boilers at the present time? 

Ans. — Oxidation of the plates, which results from 
contact with moisture and air, either carried in with the 
feed-water, or existing in the atmosphere when the boilers 
are empty. 

Ques. 444. — What conditions must exist in order that 
corrosion shall take place from this cause? 

Ans. — The simultaneous presence of both air and 
water, because neither dry air nor fresh water in which 
there is absolutely no air has any chemical action on steel 
or iron. Air dissolved in water is especially active, and 
the action is increased by the presence of various 
chlorides, such as magnesium and sodium. 

Ques. 445. — Are there any other causes that tend 
toward the corrosion of boilers, internally? 

Ans. — There are; for instance, hot sea-water, even 
when entirely deprived of air, has some action on steel 
and iron. It has been found that at the high tempera- 
tures now common in boilers, the chloride of magnesium 
contained in sea-water is decomposed by the heat and 



170 QUESTIONS AND ANSWERS 

gives ofif hydrochloric acid, the evolution of acid being 
accelerated with increase of density. 

Ques. 446. — Should sea-water be admitted to boilers if 
it is possible to prevent it? 

Ans.- — It should not; but if a portion is used, it is 
important that sufficient alkali, preferably lime, be 
admitted with the feed-water to render the water in the 
boilers slightly alkaline by the litmus test. 

Ques. 447. — Does galvanic action, due to differences in 
the material used in the construction of the boilers, con- 
duce towards corrosion? 

Ans. — Galvanic action is probably a minor cause of 
corrosion. 

Ques. 448. — What are some of the methods that 
may be employed for the prevention of corrosion in 
boilers? 

Ans.— First, the admittance of air into the boilers 
while at work should be prevented as much as possible. 
This may be done by having a tank, called the feed-tank, 
into which the air-pumps may discharge its water, and 
from which the feed-pumps can draw their water for sup- 
plying the boilers. The feed-pumps should be independent 
pumps, which can be so regulated in speed as to be 
always fully supplied with water and never to empty the 
feed-tank and so suck in and discharge air into the boilers. 
Second, the complete exclusion of sea-water from the 
boilers if possible. The waste of feed-water should be 
made good by evaporators and a reserve of fresh water 
in tanks. Third, mineral oils, which consist of hydrocar- 
bons only, should be used exclusively for lubrication of 



BOILKR OPERATION 



171 



all internal parts of the engines and pumps requiring 
lubrication. 

Ques. 449. — How may the injurious efifects of galvanic 
action be neutralized? 

Ans. — By the suspension of zinc slabs in various 
parts of the boiler, both below the water-line and also in 
the steam-space. Then if there be an}^ galvanic action 
the zinc slabs will be attacked instead of the material of 
the boiler itself. 





dl 



StNCiSLAB 



Fig. 110. Method op Suspending Zinc Si,abs. 

Ques. 450. — What is an important point to be 
observed when placing these zinc slabs? 

Ans. — They should be in actual bright contact with 
the material of the boiler and they should be well distrib- 
uted, so that every portion of the interior surface of the 
boiler is protected. 

Ques. 451. — What is the theory of the action of these 
zinc slabs, in preventing galvanic corrosion? 



172 



QUESTIONS AND ANSWERS 



Ans. — Zinc is an electro-positive metal, and it being 
suspended in the boiler causes the steel of the boiler to 
become electro-negative and thus any corrosive agent is 
induced to attack the zinc, leaving the steel uninjured. 



^*^ 



iimm:^ 






V 



^ 






3(b 




This preservative action can only take place v^hen the 
boilers have water in them and the zinc slabs fitted in the 
steam-space act only when the boilers are completely filled 
with water. 



CHAPTER VI 

TYPES OF ENGINES — CLASSIFICATION 

Ques. 452. — Into what three gene/al classes may 
marine and stationary engines be divided? 

Ans. — First, simple; second, compound; third, triple, 
or quadruple expansion. 

Ques. 453. — ^What causes the piston of a steam-engine 
to move back and forth in the cylinder? 




Fig. 112. Cross Compound Direct Connected Corliss Engine. 
Allis Chai^mers Co. 

Ans. — The expansive force of the steam that is 
admitted alternately behind the piston, at either end of the 
cylinder. 

Ques. 454. — Describe the action of the steam in a 
simple engine. 

Ans. — In a simple engine the steam is used in but one 
cylinder, and from thence it is exhausted, either into the 
atmosphere or into a condensor. 



174 QUESTIONS AND ANSWERS 

Ques. 455. — What is the leading characteristic of a 
compound engine? 

Ans. — In a compound engine the steam is made to do 
work in two or more cylinders befo^*^- it is allowed to 
exhaust. 

Ques. 456. — How is this accomplished? 

Ans. — The compound engine is fitted with two, and in 
some cases with three cylinders. The cylinder into which 
steam at boiler pressure is admitted is termed the high- 
pressure cylinder and is the smallest of the group, in 





Fig. 113. Tandem Compound EnGine, Buckeye Engine Co. 

diameter. The exhaust passage (or receiver) from this 
cylinder leads directly to the valve-chest of another 
cylinder, larger in diameter, termed the low-pressure 
cylinder, and thus conducts the exhaust from the high 
to the low-pressure cylinder, wherein it again serves as 
working steam, and if the cylinders are properly propor- 
tioned for the pressure, the amount of work done in each 
cylinder will be the same. 

Ques. 457. — How many kinds of compound engines 
are in use generally? 



TYPES OF ENGINES CLASSIFICATION 



17^ 



Ans. — Two kinds: First, the cross compound, in 
which the cylinders stand parallel, ea^.h having its indi- 
vidual cross-head, connecting rod, and valve-gear, and ail 
connected to a common crank-shaft; second, tandem 




compound, in which the cylinders are tandem to each 
other, and one piston rod, cross-head, connecting rod, and 
valve-gear is common to both, although each, cylinder has 



176 



QUESTIONS AND ANSWERS 



its own valve or valves for controlling the admission and 
release of the steam. 

Ques. 458. — What is implied in the expression **triple 
expansion?" 

Ans. — Triple expansion means that the steam has been 
allowed to expand through three successive stages, doing 





Fig. 115. Shows a Triple Ex- 
pansion Engine in which the 
High Pressure is Tandem with 
THE Intermediate Cylinder. 



EiG. 115a. Shows the Ordinary Ar- 
rangement oE Cylinders for a Tri- 
ple Expansion Engine. 



a fixed amount of work in each stage, before release 
occurs. 

Ques. 459. — How many cylinders are required on a 
triple-expansion engine? 

Ans. — Never less than three, and for large, high-speed 
engines it often becomes necessary to have two low* 



TYPES OF ENGINES — CLASSIFICATION 



177 



pressure cylinders, thus making a four-cylinder triple- 
expansion engine. 

Ques. 460. — Are four cylinder triple-expansion en- 
gines much in use? 

Ans. — They are in the marine service, and especially 
in the British navy, and they are also used to a large 
extent in the mercantile service. 

Ques. 461. — Describe the action of the steam in a 
quadruple-expansion engine. 

Tl^ ^^ „ . 




im — im — [m — etu 



Fig, 116. Arrangement of Four Cylinder Triple Expansion Engine 
FOR Marine Service. 



Ans. — In a quadruple-expansion engine, the expansion 
of the steam is divided up into four stages by causing it 
to pass through four successive cylinders, termed 
respectively the high-pressure, first intermediate, second 
intermediate, and low-pressure. In some of the larger 
engines of this type there are two low-pressure cylinders, 
thus making five cylinders in all. 

Ques. 462. — What pressures of steam are usually 
used in this type of engine? 



;78 



QUESTIONS AND ANSWERS 



Ans. — From 200 to 250 pounds per square inch. 
Ques. 463. — What are some of the advantages that 
ire to be gained in the use of steam by stage expansion? 




TYPES OF ENGINES CLASSIFICATION 179 

Ans. — First, that the cylinder into which steam 
directly from the boiler is admitted is never open to the 
cooling influence of the atmosphere, or condensor, hence 
there is not so much cooling and condensation of the 
entering steam; second, the steam that is condensed and 
reevaporated in the first cylinder reappears as working 
steam in the second cylinder; third, the loss from con- 
densation in the second and third cylinders is also reduced, 
owing to the smaller range of temperature, between 
admission and exhaust in those cylinders. 

Ques. 464. — What are the mechanical advantages of 
compound and triple-expansion engines, for heavy duty? 

Ans. — First, the facility with which high rates of 
expansion may be carried out without bringing excessive 
strains and stresses on the framing of the engine; second, 
a greater uniformity of twisting moment on the shaft. 

Ques. 465. — What are the usual ratios of cylinder 
volumes in compound and triple and quadruple-expansion 
engines? 

Ans. — For compound engines 1 to 4 between high and 
low-pressure cylinders. For triple-expansion engines, 
the ratios are about 1, 3 and 7, for high, intermediate 
and low-pressure cylinders. For quadruple-expansion 
engines the ratios are as follows: 1, 2, 4^ and 10/4 for 
high-pressure, first intermediate, second intermediate and 
low-pressure respectively. 

Ques. 466. — What is meant by the term receiver, as 
used in connection with the stage-expansion of steam? 

Ans. — In the cage of a compound engine the receiver 
is the whole of the space between the high-pressure 



180 



OUESTIOXS AND ANSWERS 



piston, when at the end of its stroke, and the back of the 
low-pressure steam-valve, whether it be slide rotative, or 
piston-valve. In the case of a triple-expansion engine, 
the space between the piston at the end of its stroke and 
the back of the intermediate steam-valve is called the 
intermediate receiver, and the space between the inter- 



> »^". T tl - AV»<.tU «| .k .UHU Ul S 







Fig. 118. Sectional Vikw ov Tandem Compound Cylinders, Showing 
Arrangement oe Steam Chests and Valves. 

mediate piston at the end of its stroke and the low-pres- 
sure steam-valve is the low-pressure receiver. 

Ques. 467. — What is the usual volume of these 
receivers in modern practice? 

Ans. — After many experiments with large reservoirs 
as receivers, it has been found that all that is necessary 
is a comparatively large exhaust pipe from the exhaust 



TYPES OF ENGINES — CLASSIFICATION 



181 



orifice of the high-pressure cylinder to the steam inlet of 
the next lower pressure cylinder, it having been demon- 
strated that the volume of the exhaust passage and pipe 
from the high-pressure cylinder and the low-pressure 
valve-chest supplied sufficient space to allow for the com- 
pression that occurs between release from the high-pres- 
sure cylinder and admission to the low-pressure cylinder. 
JromM\l£J^ Q"^^- 468.— Does this law 
apply in the case of triple and 
quadruple-expansion engines? 
Ans. — It does. 
Ques. 469. — Upon what 
does the power of any stage- 
expansion engine depend? 

Ans. — The power of a 
stage-expansion engine work- 
ing at any given rate of ex- 
pansion depends entirely upon 
the dimension of its low- 
pressure cylinder or cylinders, 
Fig. 119. Tandem Quadrupi^e Kx- ^^d is not affected by the size 

PANSiON Marine Engine Showing " ^ -^ 

Arrangement oeCyunders. ^j j^^ high-pressure Cylinder, 
which latter, in fact, carries out but one stage in the 
expansion. 

Ques. 470. — What does the capacity of the low-pres- 
sure cylinder or cylinders of such an engine require to be? 

Ans. — The same as that of the whole of the cylinders 
of a simple engine of the same power, working at the 
same initial pressure and total ratio of expansiom. 

Ques. 471.— Why is this? 




182 



QUESTIONS AND ANSWERS 



Ans. — For the reason that, since the initial pressures 
and ratios of expansion are the same in bot.i engines, it 
follows that the terminal pressures and volumes must 
also be identical in both cases. In the simple engine the 
whole of the steam at the end of the stroke fills all of the 
cylinders, while in the compound engine it is contained in 
the low-pressure cylinder or cylinders only, hence the 
capacity of this cylinder must be equal to the capacity of 
all the cylinders of the simple engine. 



r 



7t 



L.fi 



^O 



i^I.P 






2Sf/.P 



^ ^ •' — + — 'i' ■ ■ ■ / ' ^ ■■ "■■ ' 

xprrirfii I I, 



y 



H.P. 



FROM Boiuen 



Fig. 119a. Quadruple Expansion Engine, with Cylinders as Ordinariw 

Arranged — Arrows Show Course Taken by the Steam. 



Ques. 472. — Why is it necessary in some cases to 
employ two low-pressure cylinders? 

Ans. — For the reason that in very large engines one 
low-pressure cylinder would be too large and unwieldy, 
therefore it is divided into two equal parts. 

Ques. 473. — Are compound and triple-expansion 
engines much in use outside of the marine service? 

Ans. — They are to a large extent, owing to the great 
gain in economy over the simple engine. Practically all 
large manufacturing plants u^-^ them. 



TYPES OF ENGINES CLASSIFICATION 



183 



Ques. 474. — What other types of engines are in use 
in the marine service? 

Ans. — The vertical walking-beam engine is largely in 
use on the lakes, bays, and rivers of the United States. 




FiGo 120. BEI.LEVILI.E Reducing VaI^vK. 



Ques. 475. — ^^What is the leading characteristic of this 
type of engine? 

Ans. — It has usually but a single cylinder^ with a very 



184 



QUESTIONS AND ANSWERS 



long stroke in proportion to its diameter, the length of 
the stroke varying from 7 to 12 feet. 

Ques. 476. — What pressures of steam are usually 
employed in beam engines? 

Ans. — Owing to the fact that the steam is expanded 
in a single cylinder only, the pressure carried is low — 50 
to 60 pounds per square inch. 

Ques. 477. — Mention another type of engine that is in 
common use on Western rivers. 




Fig. 121. 

Fig. 121 is a sectional view of the cylinder, steam, and exhaust-chests, and 
the valve-chambers of a Corliss engine. 1 and 2 are the steam-valves and 3 and 
4 the exhaust-valves. The valves work in cylindrical chambers accurately bored 
•ut, the face of the valve being turned off to fit steam tight. They are what is 
♦'»rmed rotative valves, that is, they receive a semi-rotary motion from the wrist- 
-late, which in turn is actuated by the eccentric. 



Ans. — The stern-wheel engine, consisting of a pair of 
engines, one cylinder on either side of the boat, and 
directly connected to the shaft of the stern-wheel. Like 
the beam engine, the stroke is long in proportion to the 
cylinder diameter. 

yues. 478. — Are these engines simple or compound? 

Ans. — In former years simple engines were used alto* 



TYPES OF ENGINES — CLASSIFICATION 



185 



gether, but the later types are compound, either tandem 
or cross-compound. 

Ques. 479. — What styles of valves and valve-gears 
are in use on these engines? 

Ans. — Poppet-valves, actuated by long cam-driven 
levers, are the most generally used. Other styles of 
valves, such as rotative valves, common slide and piston- 
valves, are also quite frequently used. 
^ 



^ 


"^^ 




« 


\ 


>y>e 


c. 




<^ 


^ 


^ 




B 

i 


1 


( ® ) 


11 


C 




"0"! 


3 




<^| 


? 






_^ 


■ 


jifia 


^* \\ 


km 




ss^ 





M 






\ 


1 



Fig. 122. 

The valve-gear of a Corliss engine with a single eccentric is shown in Fig. 122. 
The connections of the exhaust-valves with the wrist-plate are positive, and 
the travel of these valves is fixed, being a constant quantity, but the connections 
of the steam-valves with the wrist-olate are detachable, being under the control 
of the governor. 



Ques. 480. — What is meant in speaking of a foi' 
valve engine? 

Ans. — An engine having two steam-valves and tW3 
exhaust-valves located near each end of the cylinder. 

Ques. 481. — What type of four-valve engine has met 
with great favor since its introduction? 

Ans.— The Corliss engine, invented by Mr. Geo. IL 
Corliss, of Providence, R. I. 



186 



QUESTIONS AND ANSWERS 



Ques. 482. — What advantage does the four-valve 
engine possess over the single-valve type? 

Ans. — The advantage that each valve may be adjusted 
to a certain degree independently of the others, the steam- 
valves tor admission and cut-off and the exhaust-valves 
for compression and release. 

Ques. 483. — What is one of the oldest forms of valve, 
and one that is still used extensively, especially on 
marine engines? 

Ans. — The D slide-valve. 




Fig. 123. 

Fig. 123 represents a slide-valve at mid-travel. S P— S P are the steam- 
ports and E P is the exhaust-port; the projections marked x at each foot of 
the arch inside the valve represent inside lap, and may be added to or taken 
from the inside edges of the valve, according as more or less compression is 
desired. The dotted lines O L, — O L, represent outside lap. 

Ques. 484. — ^What are the functions of the slide- 
valve? 

Ans. — It controls the admission, expansion and release 
of the steam and the closure of the exhaust. 

Ques. 485. — Upon what does the development of the 
full power of the engine and its efficient and economical 
use of steam, as well as its regular and quiet action, 
largely depend? 

Ans. — Upon the correct adjustment of its valve or 
valves. 



TYPES OF ENGINES CLASSIFICATION 187 

Ques. 486. — How is the slide-valve fitted to the 
cylinder? 

Ans. — The slide-valve has a flat face and it works on 
the corresponding flat face of the cylinder. In the 
cylinder face there are three passages called ports, the 
two smallest, called steam-ports, leading to each end of 
the cylinder, and the larger one, called the exhaust-port, 
eading to either the receiver, condensor, or the atmos- 
phere, as the case may be. The valve is contained in a 
steam-tight chest or casing, either cast with the cylinder. 




Fig. 124. 

Fig. 124 shows the slide-valve in Jthe position of lead — exhaust opening has 
also occurred at the opposite end of the cylinder. The arrows show the course 
of the steam, also the direction in which the valve is traveling. 

or bolted to it. This casing or valve-chest is filled with 
live steam while the engine is working. 

Ques. 487. — How must the slide-valve be constructed, 
in order that it may properly perform the four important 
functions of admission, cut-oflf, release, and exhaust 
closure? 

Ans.^It must have lap and lead. 

Ques. 488.— What is lap? 

Ans. — Lap is the amount that the ends of the valve 
project over the edges of the ports when the valve is at 
mid-travel. 



188 QUESTIONS AND ANSWERS 

Ques. 489. — What is steam lap, or outside lap? 

Ans. — The amount that the end of the valve projects 
over the outside edge of the steam-port. 

Ques. 490. — What is inside or exhaust lap? 

Ans. — The lap of the inside or exhaust edge of the 
valve over the inside edge of the port. 

Ques. 491.— What is lead? 

Ans. — ^The amount that the steam port is open when 
the piston is just commencing its stroke. This is the 
instant of admission. 

Ques. 493. — When is the instant of cut-off? 




/ 

Fig. 125. 
Fig. 125 shows the slide-valve at the end of its travel — full port openinf. 

Ans. — When the admission of steam to the cylinder is 
stopped by the steam edge of the valve closing the steam- 
port and the piston is pushed the balance of the stroke by 
the expansion of the steam admitted before cut-off 
occurred. 

Ques. 493. — When is the instant of compression? 

Ans. — When the two inside or exhaust edges of the 
valve coincide with the inner edges of the ports, the piston 
being near the end of its stroke and the valve at mid- 
travel. 

Ques. 494. — When is the instant of release? 



TYPES OF ENGINES — CLASSIFICATION 189 

Ans. — When the inner edge of the valve commences to 
open the steam-port to the exhaust-passage. 

Ques. 495. — What is the advantage gained by com- 
pression? 

Ans. — A portion of steam is confined ahead of the 
piston, thus forming an elastic cushion to absorb the 
momentum of the piston and other moving parts con- 
nected v^ith it and bring all to rest quietly at the end of 
the stroke. 

Ques. 496. — How may this compression be increased 
or diminished? 




Fig. 126. 

Fig. 126 illustrates the instant of cut-off. The valve is now traveling in the 
opposite direction. 

Ans.— By adding to or taking away from the inside 
lap of the valve. 

Ques. 497. — What is the object of giving a valve lead? 

Ans. — The effect of lead is to cause the engine to be 

, quick and not to lag at the beginning of the stroke. The 

live steam admitted through the lead opening also assists 

in forming a cushion for the piston at the end of the 

stroke. 

Ques. 498. — Do the principles governing the adjust- 
ment and action of the slide-valve necessarily have to be 
applied in the adjustment and action of rotative, piston. 



190 QUESTIONS AND ANSWERS 

and other forms of valves for controlling the distribution 
of steam in the cylinders of engines? 

Ans. — They do. The same general principles apply 
in all cases. 

Ques. 499. — How is motion generally imparted to the 
slide-valve or other types of valves? 

Ans. — By means of an eccentric, which is simply a cir- 
cular cast-iron or cast-steel sheave having a hole bored in 
it eccentrically with its own circumference, and large 
enough to permit of its being fitted on the engine shaft. 
The eccentric-sheave is either keyed on the shaft or held 




Fig. 127. 
Fig. 127 shows the slide-valve at the instant of compression. 

in its place by set-screws, and therefore revolves with the 
shaft. On the circumference of the eccentric, which is 
of sufficient width to present a good bearing surface, a 
ring, called the eccentric-strap, works, and attached to 
this ring is the eccentric-rod, which is either directly con- 
nected to the valve-rod, or valve-stem, or else imparts 
motion to the valve through the agency of a rocker-arm, 
and in many engines a link motion is used. The center 
of revolution of the eccentric being several inches apart 
from its center of formation, will, when the sheave 
revolves with the shaft, cause the eccentric to convert the 



TYPES OF ENGINES — CLASSIFICATION 



191 



rotary motion into a reciprocating motion, which through 
the agency of the rod is imparted to the valve or valves. 
f Ques. 500.— What is meant 

by the throw of an eccentric? 

Ans. — The distance be- 
tween the center of the eccen- 
tric-sheave and the center of 
the crank-shaft. This dis- 
tance is also called the radius 
of eccentricity. 

Ques. 501. — What is meant 
by eccentric position? 

Ans. — The location of the 
highest point of the eccentric 
relative to the center of the 
crank-pin, expressed in de- 
grees. 

Ques. 502.— What is ang- 
ular advance? 

Ans. — The distance that 
the high point of the eccentric 
is set ahead of a line at right 
angles with the crank, in other 
words, the lap angle plus the 
lead angle. 

Ques. 503. — If a valve had 

Fig. 128 shows an eccentric with .,t , i j u i. 

its strap and rod. K is the sheave, neither lap uor iead, what 

the center of which is shown at D. i , . . . r « 

A is the center of the shaft. The WOUld DQ the pOSltlOn GI the 

distance A D represents the throw of 

the eccentric and twice that distance U\crh nnint ni tVif* #»rrpnfrir 

equals the travel of the end B of the ^^*=>^^ pomt OI tnc CCCCIUFIU 

rod along the line A F. S is the ec- 

ecntric strait 




Fig. 128. 



relative to the crank? 



193 



QUESTIONS AND ANSWERS 



Ans. — It would be on a line exactly at right angles 
with the crank, as, for instance, the crank being at 
degrees, the eccentric would stand at 90 degrees. 

Ques. 504. — How is the reversing of modern marine 
engines usually effected? 

Ans. — By means of the link motion, using twc 
eccentrics. 

Ques. 505. — How many varieties 
of links are in use? 

Ans. — Three, the slotted link, 
the solid-bar link and the double- ^ 
bar link. 

Ques. 506. — Describe the slotted 
link. 

Ans. — It is a curved bar with a 
slot cut in it, in which the link-block 
is fitted. This link-block is attached •"* 
to the valve-rod by a pin, about 
which an oscillating motion of the 
block occurs. Two projectoins are 
formed on one side of the link, to 
which the eccentric rods are connected. 

Ques. 507. — Describe the solid-bar link. 

Ans — The solid-bar link consists of a simple, curved, 
rectangular bar, with eyes formed at each end, for con- 
necting the eccentric-rods. The solid bar passes through 
the block. 

Ques. 508. — What is the general plan of the double- 
bar link? 

Ans. — rit cons.l«its af a Dpir of curved steel bars joined 




Fig. 129. Slotted Link. 



TYPES OF ENGINES CLASSIFICATION 



193 



at the ends and kept a certain distance apart by distance 
pieces. Projecting pins are formed on the link-bars, two 
on each side, for the attachment of the eccentric-rods. 
The ends of the eccentric-rods are forked and contain each 
two adjustable bearings, which embrace the pins on each 
side of the link. The link-block is a steel or iron pin, 
sliding between the bars, and having projections on each 

] 




Fig. 130. Solid Bar I^ink. 

side which embrace the link-bars and through which they 
bars slide, on adjustable gun-metal liners. 

Ques. 509. — Why is it necessary that the link shou'r 
be curved? 

Ans. — For the reason that it is used not only fox 
reversing the engine, but also for working steam expan- 
sively, and therefore its shape must be such that when the 
block is in any intermediate position the center of the 
travel of the valve will always be constant, otherwise the 



194 



QUESTIONS AND ANSWERS 



distribution of the steam to the two ends of the cylinder 
would not be evenly divided. 

Ques. 510.— What is the slip of the linKi' 

Ans. — A slight oscillating movement of the link on its 
block. 

Ques. 511. — What is it that fixes the curvature of the 
link? 

Ans. — The length of the eccentric-rod; that is, the 
curve of the link is a circular arc, of a radius equal to the 



n 



/r^"! 




ti- 



OtsitiQ 



Fig. 131. Plan View of Double-Barbsd I«ins. 



distance between the center of the eccentric and center of 
the pin at the end of the rod. 

Ques. 512. — Is there a type of reversing valve-gear 
that employs but one eccentric? 

Ans. — There is, viz., the Marshall radial valve-gear. 

Ques. 513. — It there a type of reversing valve-gear inj 
which eccentrics are dispensed with? 

Ans. — There is, viz., the Joy valve-gear, by which the 
motion of the valve is derived from the connecting rod, 
through the medium of a vibrating link, one end of which 



TYPES OF ENGINES — CI-ASSIFICATION 



195 



is jointed to the connecting rod while the other end is 
constrained to move in a horizontal or vertical direction 
by the action of a radius rod. This motion is horizontal 
if the engine is a vertical engine, or vertical if the engine 
is horizontalo One end of another rod works on a pin in 
the vibrating link and near the other end of this rod is a 
fulcrum carried by a pin attached to sliding blocks on 
each side, working in sectors, which are carried by the 
reversing shaft. Motion is communicated to the valve 




Fig. 132. 



Fig. 132 shows details of the construction of the link-block for a double- 
barred link. 

from a point in the last-mentioned rddb2yond the fulcrum 
carried by the sectors attached to the reversing shaft. 

Ques. 514. — How is the forward or backward move- 
ment of the engine effected with the Joy valve-gear? 

Ans. — By inclining the sector on one or the other side 
of the center line of the reversing shaft and the point of 
cut-off and consequently the amount of expansion depends 
upon the amount of the inclination, the central position 
being mid-gear. The reversing arm moves these sectors 



196 



QUESTIONS AND ANSWERS 



to the required position. In large marine engines the 
reversing mechanism is operated by a small starting 
engine. On locomotives and small engines it is operated 
by hand. 

Ques. 515. — Mention one of the advantages possessed 
by the Joy valve-gear, over the double eccentric and link 
motion. 

Ans. — By this gear a constant lead is secured for all 
linked-up positions. 




Fig. 133. Stevenson L,ink Motion for Marine Engine. 

On the crank-shaft C there are keyed two eccentrics, one in the position to 
give ahead motion and the other in the position for astern motion. The eccentric 
rods are of equal length, and their ends are attached by working joints to the 
opposite ends of a curved link, L,. 

Ques. 516. — Is the Joy valve-gear much in use? 

Ans. — It is applied to a large number of marine 
engines and locomotives. 

Ques. 517. — How is the lifting valve-gear of the 
marine beam engine actuated? 

Ans. — By curved cams keyed to a transverse shaft 
""^Qur cams are fitted, two for steam and two for exhaust 



TYPES OF ENGINES — CLASSIFICATION 



197 



Ques. 518. — How is the oscillating movement imparted 
to the transverse shaft? 

Ans. — From rocker-arms, one on each end of the 




Fig. 134. 

The Marshall Valve-gear. The single eccentric, turning witi^ the crank, 
works the valve through a pivoted arm. The movement of the engine may be 
stopped or reversed by sliding the hand-lever on the notched quadrant. The 
loop paths show the movement of the valve rod-pin and also of the valve ia 
vertical directions for ahead or backing motion. 



198 



QUESTIONS AND ANSWERS 





Mi 



— rfcii- 




FiG. 135. 

Fig. 135 shows an elevation and plan of the latest arrangement of Joy's valve- 
gear applied to a vertical engine. In this gear eccentrics are dispensed with, and 
the movements of the slide-valve obtained from the connecting rod. The vibra- 
ting link B, jointed to the connecting rod at A, has one end constrained to move 
horizontally by the action of the radius rod C. One end of another rod, D, 
works on a pin in the vibrating link B; near the other end is a fulcrum carried 
by a pin F, attached to sliding blocks on each side working in sectors G, which 
are carried by the reversing shaft, the center line of the sector passing through 
the center of the reversing shaft. From D the motion is communicated to the 



TYPES OF ENGINES — CLASSIFICATION 199 

slide-valve rod by means of the link E, attached to a point K in the rod D beyond 
the fulcrum F. 

The forward or backward movement of the engine is governed by inclining 
the sector on one or the other side of the horizontal center line, and the amount 
of expansion depends on the amount of the inclination, the exactly central or 
horizontal position being *mid-gear.' The reversing arm F R moves these sectors 
to the required position, and its extremity R is connected to the starting engine 
H. The paths of the point A in the connecting rod, and also of the point B in 
the vibrating link, as the engine revolves, are indicated by dotted lines, as are 
also the extreme positions of the sector center lines for ahead and astern working 
respectively. The gear as drawn is in the stop position. By this gear a constant 
lead is secured for all linked-up positions, since when the piston is at the top or 
bottom of the stroke the pin F co-incides with the center of the reversing shaft, so 
that in this position any movement of the sectors does not affect the position of 
the slide-valve. The up and down motion of the point B therefore gives a 
constant movement of the valve equal to the lap plus the lead, while the 
horizontal motion slidmg the block to and fro in the sectors adds the amount 
required for steam opening, this amount increasing with the angle of the sector 
to the horizontal. 

transverse shaft, the pins of which are engaged by hooks 
in the eccentric-rods. 

Ques. 519. — How are the poppet-valves of the West- 
ern river boat actuated? 

Ans. — By cams very similar to those on the beam 
engine. 

Ques. 530. — Describe the construction and action of 
a double-ported slide-valve. 

Ans. — ^A double-ported slide-valve acts in a manner 
similar to a single-ported valve in the admission of steam, 
but in addition there is what is practically an inner valve, 
to which steam is admitted through passages formed in 
the body of the valve. There are also two inner ^^rts in 
addition to the two ports at the ends of the cylinder, and 
these inner ports or passages also lead to and are in cou - 
nection with the end ports. 

Ques. 531. — What is the object in using a double- 
ported valve? 

Ans. — ^To reduce the travel of the valve, which in 
large engines would be too great with a single-ported 
valve. 



300 



QUESTIONS AND ANSWERS 



Ques. 523. — ^Are treble-ported valves used to any 
large extent? 

Ans. — ^They are, on large marine engines, their action 
being on the same general principles as the double-ported 
slide-valve. 



fX/i iUST 




Fig. 136. JoY*s Assistant Cylindef* 

This consists of a small cylinder and steam-pistoi.: attached to the valve- 
spindle. The cylinder has a central inlet for steam, A, and two exhaust-ports, 
B, one for each end, leading to a common exhaust-pipe, and the piston is so 
constructed that by its motion the operations of steam admission, cut-off, release 
and compression are performed on each side of the piston. The apparatus is, 
therefore, a small engine which exercises a force on the valve to move it up or 
down, and cushions steam at each end to absorb the momentum forces. These 
assistant cylinders give diagrams similar to that of an ordinary engine; they 
exert from 15 to 25 I. H. P. each for the sizes fitted in marine engines, and the 
amount of power developed can be adjusted by means of a valve on the steam* 
pipe. If the main valve be linked in. the assistant cylinder is also automatically 
similarly affected. 



TYPES OF ENGINES CLASSIFICATION 



201 



Ques. 523. — How is the pressure of the steam on the 
back of a large, flat slide-valve lessened and relieved? 
Ans. — By relief packing rings. 

Ques. 524. — How are 
relief packing rings fitted? 
Ans. — They are some- 
times fitted on the back of 
the valve, but are generally 
fitted on the valve-chest 
cover, and are pressed out 
by springs so as to work 
steam-tight on a planed 
surface, either on the back 
of the valve or, on the in- 
side of the cover, thus re- 
ducing the area on which 
the steam-pressure can act. 
The space inside the pack- 
ing ring is connected to the 
condensor or the receiver of 
the succeeding engine, 

Ques. 525. — Do relief 
rings work in a satisfac- 
tory manner? 

Ans. — They do not, as 
a general thing, being 
troublesome to make effi- 
cient, and they also are difficult of adjustment. 

Ques. 526. — What form of slide-valve has been found 
to gire good satisfaction, especially on the high and inter- 
mediate cylinders of laree marine eneineaf 




Fig, 137. Doubi.ePorted Vai,ve. 



202 QUESTIONS AND ANSWERS 

Ans. — The piston slide-valve, consisting of two 
pistons connected together and working steam-tight in 
cylindrical chambers that contain the steam-ports. The 
face of each of the pistons corresponds to the face of the 
single- ported slide-valve, and performs the same functions, 

Ques 527. — What means are provided in large verti- 
cal engines for preventing the weight of the slide-valve, 
rod, and link gear from bearing upon the eccentric? 

Ans. — Balancing pistons, working in small steam- 
cylinders in the top end of the valve-casing. 

Ques. 528. — What is meant by setting the valve, or 
valves of an engine.? 

Ans. — The adjustment and securing of the slide-valve 
in its proper position on the rod so as to secure the 
correct distribution of the steam in the cylinder. This 
also includes the fixing of the eccentric in its correct 
position on the shaft. 

Ques. 529. — What is the first, or one of the first, 
moves in valve- setting? 

Ans. — The rods and gear are first coupled together, 
and the crank is placed on the dead center. 

Ques. 530. — What is the meaning of the expression 
dead center? 

Ans. — An engine is on the dead center when the crank 
is in line with the piston-rod, that is, when the centers of 
the crank-shaft, crank-pin. and cross-head pin are exactly 
in line, so that the pressure of the steam on the piston 
exerts no turning moment on the shaft, but produces only 
direct thrust, subjecting the shaft to bending action only. 

Ques. 531. — ^With the engine on the dead center and 



TYPES OF ENGINES — CLASSIFICATION 203 

the rods and valve-gear all coupled up, what is the next 
move in valve-setting? 

Ans. — ^The slide-valve, by means of screws and nuts 
on the valve-rod, is fixed in the proper position to give 
the required lead for the corresponding end of the cylinder. 
The shaft is then turned around until the crank is on the 
opposite dead point and the lead of the valve for that 
end of the cylinder is measured. If the amounts of lead 
at the opposite ends are different, the position of the slide- 
valve on the rod should be adjusted by means of the nuts 
and screws, until the leads are either equal, or differ by 
the desired amount. The valve should then be perma- 
nently secured on the rod, so that its position may not 
alter. This is called equalizing the lead. 

Ques. 532. — If, after having gotten the lead equalized, 
it is found that there is too much or too little, how may 
it be decreased, or increased without altering the position 
of the valve on the rod? 

Ans. — ^To decrease the lead, reduce the angular 
advance of the eccentric, and to increase the lead it is 
necessary to increase the angular advance. 

Ques. 533. — What is the rule generally observed 
regarding the lead on large vertical engines? 

Ans. — In vertical engines, owing to the weight of the 
moving parts, the lead on the lower end is generally 
made slightly greater than the lead on the upper end, and 
more exhaust lap is allowed. In such cases the valve is 
set on the rod to give the required difference between the 
two leads. Then, if the lead be too great or too small at 
both ends, the required change may be made by moving 
the eccentric ahead or back on the shafts- 



204 



QUESTIONS AND ANSWERS 



Ques. 534. — Is the position of the eccentric on the 
shaft necessarily fixed on all types of engines? 

Ans. — It is not. Many high-class stationary engines 




Fig. 138. Piston Va^ve. 



are fitted with isochronol or inertia governors, which 
control the position of the eccentric and vary the point 



TYPES OF ENGINES — CLASSIFICATION ^05 

of cut-off according as the load on the engine is light or 
heavy, thus maintaining a regular speed. 

Ques. 535. — What types of valves are used with 
isochronol governors? 

Ans. — Slide-valves of various patterns; box-valves, 
in which the steam passes through the valve; piston 
valves, in which the steam either passes through or 
around the ends of the valve. 

Ques. 536. — In all types of reciprocating engines the 
same factors affecting the distribution of the steam are 
present. What are they? 

Ans. — Outside lap, affecting admission and cut-off, 
and inside lap, affecting release and compression. 

Ques. 537. — How are these factors distributed in the 
four-valve type of engine? 

Ans. — They are distributed among the four valves, 
each valve performing its own particular function in the 
distribution of the steam for the end of the cylinder to 
which it is attached. 

Ques. 538. — What advantage is there connected with 
setting the valves of a four-valve engine, as compared 
with a single valve? 

Ans. — Each valve may be adjusted to a certain degree 
independently of the others, thus, for instance, the steam- 
valves of a Corliss engine may be adjusted to cut off the 
steam at any point from the beginning up to one-half the 
stroke, without in the least affecting the release or com- 
pression, because these latter events are controlled by the 
exhaust-valves. 

Ques. 539.— What is the first requisite in setting the 
valves of a Corliss engine^ 



206 



QUESTIONS AND ANSWERS 



Ans. — To place the crank on the dead center. 

Ques. 540. — What is the next move? 

Ans. — To adjust the length of the hook-rod, if it is 
adjustable; if not, then the length of the eccentric-rod, 
so that the wrist-plate will vibrate equal distances each 




w 



w 



Fig. 139. Wrist Plate oe Corliss Engine. 



way from its central position, which is marked on top of 
the hub. 

Ques. 541. — How should the rocker-arm, that carries 
the eccentric-rod, and hook-roa De adjusted? 

Ans. — The length of the eccentric-rod should be such 



TYPES OF ENGINES CLASSIFICATION 



207 



that the rocker-arm will vibrate equal distances each way 
from a vertical position. 

Ques. 542. — How may the vioration of the wrist-plate 
and rocker-arm be tested? 

Ans. — By connecting the eccentric-rod and the hook- 
rod in their proper places, and turning the loose eccentric 
around on the shaft in the direction the engine is to run. 

Ques. 543. — Having gotten these important adjust- 
ments correctly made, what is the next step in setting 
Corliss valves? 

Ans. — Remove the back bonnets from the four valve 




Fig. 140. Steam-Vai.ve of Corliss Engine. 



chests, and while neither the working edges of the valves 
nor the ports can be seen, yet certain marks will be found 
on the ends of the valves and corresponding marks on the 
faces of the chests, which serve as a guide "in setting the 
valves. 

Ques. 544. — Having removed the bonnets and found 
the marks, what is to be done next? 

Ans. — Temporarily secure the wrist-plate in its 
central position by tightening one of the set-screws on 
the eccentric. Then connect the valve-rods to the wrist- 



208 



QUESTIONS AND ANSWERS 



plate and to the small crank-arms attached to the ends of 
the valves, adjusting^ their lengths so that the steam- 
valves will have from /4 to f% inch lap, and the exhaust 
valves from ^V to tV inch opening. 

Ques. 545. — In adjusting the steam- valves, what par" 
ticular detail should be carefully noted? 

Ans. — The direction in which the valves turn to open 
should be noted. In most Corliss engines the arm of the 
small crank to which the valve-rod is connected, extends 



( 


\ ; 


> r 


1 r-r. ^ 


1 




/ : 


/ ^ 


^=^ 



Fig. 141. E^xkaust-VaIvVE o^ Cori:,iss Engine. 



downwards from the valve-stem. This will cause the 
valve to move towards the wrist-plate in opening. 

Ques. 546. — After the valve-rods have been properly 
adjusted as to length, what is the next move? 

Ans. — -Place the engine on the dead center — either 
center will do — and move the eccentric around on the 
shaft in the direction the engine is to run, until the 
eccentric is far enough ahead of the crank to allow the 
steam-valve for that end of the cylinder the proper 
amount of lead opening, which will vary according to the 
size of the engine. Then tighten the eccentric set screws 



TYPES ^1^ ENGINES— CLASSIFICATION 



209 



and ^rrn the engine around to the opposite center and 
note whether the lead is the same on both ends. 

Ques. 547. — In case there is a difference in the lead 
for the two ends, how may it generally be equalized? 
- Ans. — By slightly altering the length of one of the 
valve-rods. 

Ques, 548. — What is the next point to receive atten- 
tion, in setting Corliss valves? 

TABLE 8 

LAP AND LEAD OF CORLISS VALVES 



Size of Engine. 


Lap of Steam 


Lead Opening of 


Lead Opening of 


Valve. 


Steam Valve. 


Exliaust Valve. 


12 inches 


J inch 


a^ inch 


A inch 


14 " 


A " 


5^ " 


s'l " 


i6 •• 


tV " 


A " 


^ " 


i8 


1 " 


h " 


A " 


20 " 


1 '• 


A " 


A " 


22 " 


1 " 


^'' 


iV •' 


24 " 


i\ " 


A " 


ft •• 


26 " 


A " 


*^ ' 


ft " 


28 " 


/. " 


»^ 


%% :: 


30 " 


i '• 


s\ " 




32 


J " 


"^* " 




34 •' 


i '■ 




i ** 


36 •' 


i " 


i " 


4" ** 


38 •• 


l-B " 


" 


^« !! 


40 


ft " 


i " 


A " 


42 


A " 


1 


A " 



Ans. — The adjustment of the lengths of the^ rods 
extending from the governor to the releasing mechanism^ 
so that the valves will cut off at equal points in the 
stroke. 

Ques. 549. — How is this adjustment accomplished? 

Ans. — By raising the ^^ok-rod clear of the wrist-plate 
pin and with the bar provided for the purpose, move the 



210 QUESTIONS AND ANSWERS 

wrist-plate to either one of its extreme positions, as 
shown by the marks on the hub, and, holding it in this 
position, adjust the length of the governor-rod for that 
steam-valve (which will then be wide open) so that the 
boss or roller which trips the releasing mechanism is just 
in contact, or within ^V inch of it. Then move the wrist- 
plate to the other extreme of its travel and adjust the 
length of the other rod in the same manner. 

Ques. 550. — How may the accuracy of this adjust- 
ment be tested? 

Ans. — Raise the governor-balls to their medium 
position, or about where they would be when the engine 
is running at its normal speed, and block them there. 
Then having again connected the hook-rod to the wrist- 
plate, turn the engine around in the direction in which it 
is to run, and when the valve is released by the trip, 
measure the distance upon the guide that the cross-head 
has traveled from the end of the stroke. Now continue 
to turn the engine in the same direction until the other 
valve is released, and measure the distance that the cross- 
head has traveled from the opposite end of the stroke, 
and if these two distances are the same, the cut-off is 
equalized. If there is a difference, lengthen one rod and 
shorten the other until the point of cut-off is the same for 
both ends. The lengths of the dash-pot rods should also 
be adjusted, so that when the plunger is at the bottom of 
the dash-pot the valve-lever will engage the hook. The 
io«k-nuts on all rods should then be securely tightened. 



CHAPTER VII 

CONDENSERS — AIR-PUMPS — SEA- WATER 

Ques. 551. — What is the average composition of sea- 
water? 

Ans. — Sea-water contains about ^^2 part of its weight 
of solid matter, of which common salt (sodic chloride) is 
the principle constituent. The average composition of 
the solid matter in sea-water may be taken as follows: 

Sodic chloride, or common salt > 76 per cent 

Magnesic chloride . .10 

Calcic sulphate, or gypsum ..•••• 5 

Magnesic sulphate 6 

Carbonate of lime, and organic matter. 3 

Ques. 552. — Does the common salt in sea-water cause 
much trouble for the marine engineer? 

Ans. — It does not, for the reason that it remains 
soluble in water at all temperatures, and there is no 
deposit of salt, except under extreme circumstances. 

Ques. 553. — What is the principal scale-forming 
ingredient in sea-water? 

Ans. — ^ulphate of lime, or calcic sulphate. Deposit 
is also formed by sulphate of magnesia, although it is less 
objectionable than the lime deposit. 

Ques. 554. — At what temperature does the sulphate 

of lime become insoluble in water and form a deposit on 

the boiler plates? 

Ans. — ^At a temperature of 280 degrees to 295 degrees 
211 



212 QUESTIONS AND ANSWERS 

Fahrenheit, corresponding to a pressure of 35 to 
45 pounds pressure of steam by the gauge. As the tem- 
perature of the water rises, the other sulphates become 
insoluble, and at 350 degrees Fahrenheit, or 120 pounds 
gauge-pressure, sea-water is incapable of holding any 
sulphates in solution. 

Ques. 555. — What other cause, besides a high tempera- 
ture, tends to precipitate these salts? 

Ans. — Increase of density, caused by evaporation of 
the water, even if the temperature remains about 
212 degrees Fahrenheit. Sulphate of calcium is thus 
deposited at a density of /f. Common salt does not 
crystallize out until a density of about g^j is reached. 

Ques. 556. — When was it possible to use sea-water 
for feeding boilers? 

Ans. — In the early days of marine engineering, when 
a low-pressure (35 to 45 pounds) was carried, and the 
jet condenser was used, in which the steam was exhausted 
into the condensing chamber, where it came into actual 
contact with and was condensed by a jet of cold sea- 
water. The feed-water for the boilers was drawn from 
this mixture of sea-water and condensed steam, conse- 
quently a large quantity of sea-water was sent into the 
boilers, but as the temperature was low and the density 
was not allowed to exceed /g^, the salts were held in 
solution fairly well. 

Ques. 557. — How was the increase of density pre- 
vented? 

Ans. — By blowing off a portion of the denser boiler- 
water at stated times, and making up the loss by ad- 



CX)NDENSERS — ^.\IR-PUMPS — SEA-WATER 313 

mitting a larger quantity of salt water. This was termed 

* 'brining the boiler.*' 

Ques. 558. — What led to the introduction of the 
surface condenser? 

' Ans. — With the advent of high pressures, it was 
found impossible to prevent the deposit of scale, and all 
of its attendant evils. It was therefore found necessary 
to condense the exhaust steam without bringing it into 
actual contact with the condensing water, hence the sur- 
face condenser was designed. 

Ques. 559. — Mention two of the principal advantages 
gained by the use of the surface condenser. 

Ans. — First, by its use fresh feed-water is obtained 
for the boilers; second, the condition of the condensing 
water is of no importance, as regards the feed-water so 
that, no matter whether it is salt, muddy, acid, or other- 
wise impure, pure water is always obtained for the 
boilers, provided the condenser is maintained in good 
condition and no leakage is allowed to occur. 

Ques. 560. — What is the meaning of the word 
vacuum? 

Ans. — That condition existing within a closed vessel 
during the absence of all pressure, including atmospheric 
pressure. 

Ques. 561. — How is a vacuum measured? 

Ans. — It is measured in inches of a column of mer- 
cury contained within a glass tube a little more than 
30 inches in height, having its lower end open and immersed 
in a small open vessel filled with mercury. The upper 
end of the glass tube is connected with the vessel in which 



214 QUESTIONS AND ANSWERS 

the vacuum is to be produced. When no vacuum exists, 
the mercury will leave the tube and fill the lower vessel. 
When a vacuum is maintained within the condenser, or 
other vessel, the mercury will rise in the glass tube to a 
height corresponding to the degree of vacuum. If the 
mercury rises to a height of 30 inches it indicates a per- 
fect vacuum, which means the absence of all pressure 
within the vessel, but this condition is never realized 
in practice, the nearest approach to it being about 
28 inches. 

Ques. 562. — Is the mercurial vacuum-gauge used in 
every-day practice? 

Ans. — For purposes of convenience it is not generally 
used, it having been replaced by the Bourdon Spring- 
gauge, although the mercury-gauge is used for testing. 

Ques. 563. — ^^What is the advantage, from a purely 
economic standpoint, in allowing the exhaust steam to 
pass into a condenser in which a vacuum is maintained 
rather than to allow it to exhaust into the open air? 

Ans. — In a non-condensing engine, that is, an engine 
in which the exhaust steam passes into the open air, the 
pressure of the atmosphere, amounting to 14.7 pounds 
per square inch at sea-level, is constantly in resistance to 
the motion of the piston. Therefore the exhaust or ter- 
minal pressure can not fall below the atmospheric pres- 
sure and is generally from 2 to 5 pounds above it, caused 
by the resistance of bends, and turns in the exhaust pipe, 
or other causes which tend to retard the free passage of the 
steam. On the other hand, if the steam were allowed to 
exhaust into a condenser in which a vacuum of 25 inches 



CONDENSERS AIR-PU M PS SEA- WATER 



215 



is being maintained, the terminal pressure or back pres- 
sure in resistance to the forward motion of the piston 
would be but 2.5 pounds, and if a vacuum of 28 inches 
existed in the condenser there would be practically no 
back pressure, thus making available for useful work the 
14.7 pounds of steam which in the non-condensing engine 
was required to overcome the resistance of the atmos- 
pheric pressure. 

Ques. 564. — Is it proper, then, 
to consider the vacuum in a con- 
denser as power? 

Ans. — The vacuum can not be 
considered as power at all. It oc- 
cupies the anomalous position of 
increasing, by its presence, the ca- 
pacity of the engine for doing work. 

Ques. 565. — How is the vacuum 
in a condenser usually maintained? 

Ans. — By a pump called an air- 
pump, although a partial vacuum 
can be produced by the mere conden- 
sation of the exhaust steam as it enters the condenser, by 
allowing a spray of cold water to strike it. The steam when 
it first enters the condenser drives out the air and the vessel 
is filled with steam at a low pressure, which, when con- 
densed, occupies about 1,600 times less space than it did be- 
fore being condensed, hence a partial vacuum is produced. 
The action of the siphon injector is based upon this principle. 

Ques. 566. — Describe the construction and action of 
the siphon condenser. 




Fig. 142. 
Siphon Condenser. 



tl6 



QUESTIONS AND ANSWERS 



Ans. — The siphon condenser is a form of jet condenser 
in which no air-pump is used. In this type of condenser 
the supply of condensing water is drawn from outside 
pressure, either from an overhead tank, or other source. 




Fig. 143. Knowi^es Jet Condenser. 



and passing into an annular enlargement of the exhaust- 
pipe, is discharged downwards in the form of a cylindrical 
sheet of water, into a nozzle which gradually contracts. 
The exhaust steam, entering at the same time^ is con- 



CONDENSERS AIR-PUMPS SEA- WATER 



217 



densed and the contracting neck of the cone-shaped nozzle 
gradually brings the water to a solid jet and it rushes 
through the nozzle with a velocity sufficient to create a 
vacuum. This type of condenser can only be used where 
the discharge pipe has a perfectly free outlet. 

Ques. 567. — Describe in general terms the construc- 
tion and action of the jet condenser. 

Ans. — The jet condenser is usually a vertical,cylindri- 




/i£r/^Suzn£> 



Fig. 144. Section Ai, View oi? a SurPacb Condenser and Independent Air 
AND C1RCU1.ATING Pumps. 



cal, cast-iron vessel, made air-tight, and which receives 
the exhaust steam from the low-pressure cylinder. In 
modern plants, condenser-shells are often made of sheet 
steel in cylindrical shape, reenf orced with stiflfening rings. 
The exhaust steam enters at the top and the condensing 
water enters usually at the side, flowing in through the 
spraying nozzle, and, discharging through a large num- 
ber of small holes, comes in contact with the steam in the 



318 QUESTIONS AND ANSWERS 

form of spray, thus producing a quick condensation while 
falling to the bottom of the condenser, to be drawn off by 
the air-pump. A cock or valve is fitted in the injection 
pipe, for the purpose of regulating the supply of cooling 
water. 

Ques. 568.— Why is an air-pump a necessary part of a 
reliable jet-condensing apparatus? 

Ans. — The mixture of condensing water and con- 
densed steam must be pumped away constantly, also the 
condensing water always contains a certain volume of 
air in solution, which may be liberated, either by boiling 
it or by reducing the pressure to which it is subjected. 
This air is liberated in the condenser, and if it is not 
pumped away regularly, it is liable to accumulate and 
spoil the vacuum. 

Ques. 569. — How may the dimensions of a single-act- 
ing air-pump for a given sized engine be determined? 

Ans. — In the solution of this problem, two factors 
must be considered: First, the total volume of the low- 
pressure cylinder; second, the density of the exhaust 
steam. The volume of the air-pump cylinder is then 
found by the following rule: Multiply the volume of the 
low-pressure cylinder in cubic feet by 3.5, and divide the 
product by the number of cubic feet contained in 1 pound 
weight of exhaust steam at the pressure at which it 
enters the condenser. This rule applies only to jet con- 
densers. 

Ques. 570. — Describe the construction and action of 
the surface condenser. 

Ans. — The surface condenser, like the jet condenser. 



CONDENSERS — AIR-PUMPS — SEA- WATER 



219 



is an air-ti^ht iron or steel vessel, either cylindrical or 
rectangular in shape, but, unlike the jet condenser, it is 
fitted with a large number of brass or copper tubes of 
small diameter (generally about H inches), through which 
cold water is forced by a pump called a circulating 




Fig. 145. 



Side view of large cylindrical horizontal surface-condenser having two 
exhaust-inlets. The tubes are not shown. The steam enters at the orifices marked 
A, and is withdrawn, when condensed, through the orifice B by the air-pump. 
The circulating water enters at C, and is confined by the diaphragm D to the 
lower half of the tubes, and, having traversed these tubes, it returns through the 
upper half of the tubes, being finally discharged to the sea through the pipe E).; 
T. T. are the tube-plates near the ends of the condenser casing. 

pump. A vacuum is maintained in the body of the con- 
denser by the air-pump, and the steam exhausting into 
this vacuum is condensed by coming in contact with the 
cool surface of the tubes. Or, as is often the case, the 
exhaust steam passes through the tubes instead of around 



220 



QUESTIONS AND ANSWERS 



them, and the cooling water is forced into and through 
the body of the condenser, the vacuum in this case being 
maintained in the tubes. The tubes may be placed either 
vertical or horizontal. When the steam is passed through 
the tubes, they are generally placed vertical, while, on the 




T'iG. 14(5. "Ewo Sectional \ iew o^ Cylindrical Horizontai, Sur^aCC 

Condenser, Showing a Portion o? the Tubes. 

other hand, if the water circulates through them they are 
placed horkontal. The system of causing the water to 
circulate through the tubes, the steam surrounding them, 
is the more general. 



CONDENSERS — AIR-PUMPS — SEA- WATER 



221 



Ques. 571. — How are the tubes generally arranged in 
a surface condenser? 

Ans. — They are arranged in one or more systems, so 
that the condensing water passes through the condenser, 
usually twice, the coldest water entering at the bottom 
and coming in contact with the steam at its lowest tem- 
perature, and the warmest water at the top meeting the 

hottest steam. The exhaust 
steam enters at the top and 
after passing over the cold 
tubes is removed in the form 
of water, by the air-pump. 
The steam is directed in its 
downward course by baffle- 
plates, thus securing complete 
utilization of the cooling sur- 
face. A space is provided at 
the bottom of the condenser 
for the accumulation of the 
water of condensation below 
the cooling surface. The con- 
denser casing or shell for naval 
vessels is either cast in brass or else built up from com- 
position sheets, in order to save weight and prevent cor- 
rosion and galvanic action, which would be more liable 
to take place with an iron or steel shell. 

Ques. 572. — How are thetuLes secured in their places? 

Ans. — Brass or composition tube-plates are placed in 

the shell, near each end, sufficient space beine^ left 

between the outside cover-plates and the tube-plates iu» 




Fig. 147. Details ot Wick and 
Gland Packing for the Tubes 
o? A Surface Condenser. 



222 



QUESTIONS AND ANSWERS 



the Circulation of the cooling water. Into these plates, 
which are thick enough to furnish a good bearing for the 
tubes, the ends of the tubes are fitted and packed thor- 
oughly tight, sometimes with a wood packing, sometimes 
with small screwed stuffing boxes with glands and fol- 
lowers, which tighten upon wick packing. The wood 
packing consists of a small soft wooden sleeve, which is 
forced into the small hole over the tube end in a dry 
state, and after becoming wet it swells and clamps the 




Fig. 148. Method of Packing Tubes of a Worthington Surface Condenser. 

One end of each tube is flanged and rigidly held in the tube head by means 
of a screw follower; the other end of the tube passes through an adjustable 
gland, which permits of free movement of the tube during expansion and 
contraction. This method of securing rigidly one end of the tube reduces the 
number of glands or stuffing-boxes to just one-half the number found in ordin- 
ary condensers. The glands can be readily removed and the packing replaced 
if it becomes leaky from long use. 

tube, thus forming and preserving a tight joint so long 
as it is kept wet. 

Ques. 573. — Which kind of packing is the most reli- 
able for condenser tubes? 

Ans. — The gland and wick, for the reason that it 
always remains tight, while on the other hand the wood 
packing will shrink and become loose if the condenser is 
out of service for a time. . 



CONDENSERS — AIR-PUMPS — SEA- WATER 223 

Ques. 574. — ^What are the usual dimensions of the 
£ubes of surface condensers? 

Ans. — They are generally about ^ inches in diameter, 
are made of brass, about ^\ of an inch thick, of a com- 
position consisting of not less than 70 per cent of coppei 
and not less than 1 per cent of tin, the remainder being 
zinc, the small quantity of tin being added to prevent 
galvanic action. The tubes are pitched not less than f i 




Fig. 149. WoRTHiNGTON Surface Condenser, with Air and CirculaTin* 

Pump. 

inches apart in order to allow sufficient material for the 
gland. They are zigzagged so as to occupy as small a 
volume as possible. Condenser tubes vary considerably 
in length, depending upon the size of the condenser, the 
usual length in large condensers being from 8 to 10 feet, 
while in some very large condensers the tubes are 14 or 
15 feet in length. The tube-plates are about 1 inch thick, 
in order to provide sufficient depth for the gland and 
packing for the tubes* 



«24 



QUESTIONS AND ANSWERS 



Ques. 575. — ^What type of air-pump is generally used? 
Ans. — ^The vertical single-acting air-pump has been 



cover rtmoveal. 




Fig. 150. 

Section of Blake independent air-pump, fitted in many vessels, including 
several U. S. warships. There are two steam-cylinders and two single acting 
vertical air-pumps of the usual type. It works at slow speed and gives excel- 
lent results. 



CONDENSERS AIR-PUMPS SSA-VVATER 225 

found to be the most efficient. In vertical engines the air- 
pump generally receives its motion from the cross- 
head of the engine, through the medium of a short 
walking-beam. There are, however, a great many 
engines fitted up with an independent air-pump and 
condenser, in which the air-pump is simply an ordinary 
double-acting steam-pump, having its own steam* 
cylinder, and may be operated independently of the engine, 
which is a great advantage, as there is not so much 
danger of the water from the condenser backing up into 
the cylinder in case of a sudden shut-down of the engine, 
which is liable to occur with a jet condenser. 

Ques. 576. — Describe the parts of the vertical single- 
acting air-pump. 

Ans.— It consists of the barrel, or cylinder, the suc- 
tion-channel way at the bottom, the cover, with delivery- 
channel way and the hot well, the whole being made air- 
tight. The moving parts are the bucket, or piston, with 
its valves, the foot-valves and the head-valves. 

Ques. 577. — Describe the arrangement of the air- 
pump in connection with the condenser. 

Ans. — The suction-channel way is in connection with 
the lowest part of the condenser, in order that the water 
can be readily and completely removed from the condenser. 
It usually supports the foot-valves and all joints and! 
valve-seat division-plates require to be fitted air-tight. 
The barrel is generally connected to a flange or facing of 
the suction-channel way, and it is constructed of com- 
position or cast iron with a composition sleeve pressed in 
and bored out truly cylindrical, in order to form a jmooth 



226 



QUESTIONS AND ANSWERS 



and durable working-cylinder fo:: the buckc jr piston, 
which is kept tight against the barrel, either by water- 




Fig. 151. Sectionai, View oe Verticai, Singi^e Acting Air-pump. 



grroov*-s, or, more commonly, by packing, consisting of 
.me '^r more split metallic packing rings. Sometimes 



CONDENSERS — ^AIR-PUMPS — SEA-WATER 



22^: 



Guard 







Seating 



fibrous soft packing, held in place and compressed by a 
follower ring, is used. A stuffing box is provided in the 
top cover, through which the piston-rod or trunk, as the 
case may be, has water-tight passage. 

Ques. 578. — What kind of valves are used in air- 
pumps? 

Ans. — Rubber valves, 
either of hard or soft rub- 
ber, but since the introduc- 
tion of mineral oil as a 
lubricant for the engine cyl- 
inders, it has been found 
that the ordinary rubber 
valves deteriorate under its 
influence, and metal valves 
are now largely coming into 
use, especially in the navies. 
They may be made of thin 
sheet metal, are light, and 
not affected by grease, if 
cleaned occasionally, and 
will last a long time. In 
form, air-pump valves are 
single rectangular 
flaps that lift on one edge 
against a curved metallic guard, or else there are a number 
of smaller circular valves, lifting bodily from their seats, 
and secured to the seat by a central stud, which also carries 
a metal guard above the valve. The valve-seats are usually 
independent, being constructed of composition metal, and 




Fig. 152. 

Details of Rubber Vai.ve, Vai.ve- either 
SEAT AND Guard EOR Air-pump. 



328 



QUESTIONS AND ANSWERS 



pressed into their places. They are divided into small 
spaces by gratings, so that the unsupported area of the 
valve may not be too large. The bucket carries the 
bucket-valves, which allow the air and water to pass 
through to the delivery side. Air-pump valves are some- 
times fitted with spiral springs of bronze wire on top, to 
secure quick closing. The flap valves are clamped to the 
seat, on the stationary edge, by their curved guards. 

Ques. 579. — How is the bucket or piston of the air- 
pump actuated? 



GD, 



Light SpffiNGS soMermes 

FITTED HERE. ON BUCKCT 
AND fOOrVALV£S 




Fig. 153. Section of Metal Valve, Valve-seat and Guard eor Air-pump. 



Ans. — Either by a solid piston-rod, or by a hollow 
trunk, made entirely of composition, or covered by a 
composition sleeve. With the piston-rod type it is neces- 
sary to have a connecting rod and guides above the top 
cover of the air-pump, while the trunk type contains the 
connecting rod bearing in the trunk, near the bucket, and 
requires no extra guides. 

Ques. 580. — What is the function of the hot well? 

Ans. — It acts as a small reservoir, for the accumula- 
tion of the discharge- water from which the feed-pumps 



CONDENSERS AIR-PUMPS SEA-WATER 



229 



draw their supply. The later vessels in the English navy 
are fitted with **feed-tanks" in which the discharge from 
the air-pumps is allowed to accumulate, and from which 
the feed-pumps draw their supply of water for feeding 
the boilers. There is a feed-tank for each engine-room, 







Fig. 154. Worthington Central Condi:nser for a Large Stationary Pi^nt, 
Showing Pumps ^nd Piping. 



and they are connected by a pipe running between the two 
engine-rooms, fitted with a shut-off valve worked from 
either engine-room. These feed-tanks are fitted with 
glass water-gauges and zinc slabs. 



230 



QUESTIONS AND ANSWERS 



Ques. 581. — What is the function of the circulating 
pdmp in connection with the surface condenser? 




fti - 155. Transverse Section op a Centripugai. Pump. B. Casing. D D, 

Curved Vanes. 



Ans.^ — It either forces or draws the cooling watei 
through the tubes or the body of the condenser. 



CONDENSERS AIR-PUMPS SEA-WATER ^31 

Ques. 582. — What type of pump has beei* icund to be 
best adapted to this work? 

Ans. — The centrifugal pump worked by an mdepen- 
dent auxiliary engine, for the reason that the pump works 
smoothly, there are no valves, and having a separate 
engine, it can be kept working and the condensers kept 
cool when the main engines are stopped, which is not the 
case with a pump that receives its motion from the main 
engines. Another great advantage possessed by the 
independent system is, that the speed may be regulated 
so as to supply the required quantity of water. 

Ques. 583. — Describe the construction and action of 
the centrifugal circulating pump. 

Ans. — The pump consists of an impeller wheel or fan 
revolving inside a casing. The impeller and casing are 
made of gun metal, and the spindle or shaft carrying the 
impeller is either cast of gun metal in one piece with the 
impeller, or formed separately of forged bronze and keyed 
to it. This spindle runs in lignum-vitae bearings and is 
lubricated with water. The impeller generally consists 
of a central web guiding the incoming water, with two 
side-plates that gradually approach each other as they 
near the circumference and between which runs a series 
of curved vanes. These vanes are curved away from the 
direction of rotation as they proceed from the boss to the 
circumference. The water enters the central part of the 
impeller through the inlet pipe and is thrown by the 
rapidly revolving vanes outwards and around into the 
casing which surrounds the circumference of the wheel. 
The casing is of gradually increasing area and leads to 



232 



QUESTIONS AND ANSWERS 



the delivery pipe, through which it is forced by the cen- 
trifugal action to the condenser, where, after traversing 
the tubes, it is discharged overboard. The casing is 




^-r— 



Fig. 156. I/5NGITUDINAI. Section of a CENTRipuGAr, Pump. A, Centrai, Web 
C C, Side Plates. E, Inlet. F, Discharge. 

formed in two parts to enable the impeller to be inserted 
and also to facilitate insoection. 



CONDENSERS AIR-PUMPS SEA- WATER 233 

Ques. 584. — How is the quantity of water required to 
condense the exhaust steam of an engine determined? 

Ans. — The quantity of cooling water required for a 
condensing system depends primarily upon the system, 
whether it is surface condensing or whether the condenser 
is a jet condenser The surface condenser needs a greater 
quantity of water than does the jet condenser. This is 
due to the fact that in the surface condenser the water, 
not being mixed with the steam, can not absorb the heat 
so rapidly. 

Ques. 585. — About how much more water does a sur- 
face condenser require than is needed by a jet condenser? 

Ans. — About 15 per cent more. 

Ques. 586. — What three factors determine the quantity 
of cooling water required? 

Ans. — First, the density, temperature, and volume of 
the steam to be condensed in a given time; second, the 
temperature of the overflow and third, the temperature of 
the injection water. For instance, it may be desired to 
keep the overflow at as high a temperature as possible, for 
the purpose of feeding the boilers, or the temperature of 
the injection or cooling water varies greatly. It may 
be 35 degrees in the winter and 70 degrees in the summer. 
In the marine service the temperature of sea-water 
varies considerably, depending upon the locality, in the 
tropics the temperature of the sea-water in the summer 
being often as high as 85 degrees Fahrenheit. 

Ques. 587. — What quantity of condensing water would 
be required in a jet condenser into which the exhaust 
steam under an absolute pressure of 7 pounds is passing-, 



234 QUESTIONS AND ANSWERS 

assuming the temperature of the cooling water to be 
55 degrees and the temperature of the overflow to be 
110 degrees? 

Ans. — In these calculations the total heat in the steam 
must be considered. This means not only the sensible 
heat, but the latent heat also. Now in 1 pound weight of 
steam at 7 pounds absolute pressure the total heat is 
1,135.9 heat units. The temperature of the overflow being 
110 degrees, the total heat to be absorbed from each pound 
weight of steam in this case would be 1,135.9 
— 110 = 1025.9 thermal units. The temperature of the 
condensing water being 55 degrees and the temperature 
of the overflow being 110 degrees, there will be 110 
degrees — 55 degrees = 55 degrees of heat absorbed by 
each pound of cooling water passing into and through the 
condenser, and the number of pounds of water required 
to condense each pound weight of steam under these 
conditions will equal the number of times 55 is con- 
tained in 1,025.9, thus, ^jV= 18.65 pounds. Assuming 
the steam consumption of the engine to be 17 pounds per 
indicated horse-power per hour, then 17 X 18.65 = 317.05 
pounds of water is required per horse-power per hour for 
condensing purposes. 

Ques. 588. — How is the weight of cooling water 
required per hour determined, when the steam consumption 
per indicated horse-power per hour is not known? 

Ans. — In this case the volume of steam exhausted per 
hour must be considered. Thus, assume the cylinder from 
which the steam is exhausted to be 24 X 48 inches and 
the revolutions per minute to be 80. The piston dis- 



CONDENSERS AIR-PUMPS SEA-WATER 



235 



placement will equal area of piston less one-half area of 
rod, multiplied by length of stroke. The area of a circle 
24 inches in diameter = 452.39 square inches. Suppose 
the piston-rod to be 4.5 inches in diameter, its area is 
15.904 square inches, one-half of which = 7.952 square 

Table No. 9 

Jet Condensing 

Quantity of Injection Water per Revolution of Engine. 

INJECTION water 50° OVERFLOW 110° 



Low-pressure Cylinder. 


Single-cylin- 
der. Water 
per Rev. 


Two-cylinder, 

Water per 

Rev. 


Three-cylin- 
der, Water 
per Rev. 




Lbs. 


Galls. 


Lbs. 


Galls. 


Lbs. 


Galls. 


20x36 inches 


4.2 

5.1 

7. 

8.3 
11. 
12.6 
16.2 
18.3 
22.8 
25.5 
31. 
37.5 
48.5 
57. 
66. 
75.6 
85. 


.5 

.61 
.84 
1. 

1.45 
1.52 
1.95 
2.2 
2.75 
3.07 
3 73 
4.51 
5.84 
6.89 
7.9 
9. 
10. 


3.9 

4.8 

6.6 

7.8 

10.4 

n.7 

15. 

17.0 

21.2 

23.7 

28.8 

34.8 

45. 

53.1 

61.5 

70.5 

80. 


.47 
.57 
.79 
.93 
1.24 
1.41 
1.81 
205 
2.55 
285 
3.45 
4.2 
5.42 
6.4 
7.41 
8.5 
9.6 


3.6 

4.4 

6. 

7.2 

9.5 
10.8 
13.9 
15.8 
19.6 
21.9 
26.7 
322 
4L7 
49.2 
57. 
65.3 
74. 


.43 


22x36 " 


.53 


24x42 " 


.72 


26x42 " 


.87 


28x48 " 


L14 


30x48 " 


L3 


32x54 " 


1.68 


34x54 " 


L9 


36x60 " 


2.36 


38x60 " 


2.64 


40x66 " 


3.2 


44x66 " 


3.8 


48x72 " 


5. 


52x72 " 


5.9 


56x72 " 


6.8 


60x72 " 


7.8 


64x72 " 


8.9 







(Table No. 9. — From Book on Compound Engines. 
troit, Mich. ) 



By James Tribe, De- 



inches. The effective area of the piston is therefore 
452.39 — 7.953 = 444.4 square inches and the piston 
displacement equals 444.4 X 48 = 21,332.64 cubic inches. 
It is necessary in this calculation to express the total 
volume of steam exhausted per minute in cubic feet, 
therefore 21.332.64 -^ 1.728 (number of cubic inchesvin a 



236 QUESTIONS AND ANSWERS 

cubic foot) gives 12.34 cubic feet of piston displacement, 
and the engine running at a speed of 80 revolutions per 
minute will send into the condenser a volume of steam 
equal to twice the piston displacement multiplied by the 
number of revolutions per minute, expressed thus: 12.34 
X 2 X 80 = 1,974.4 cubic feet per minute. Assuming the 
absolute pressure of the exhaust to be 7 pounds per 
square inch, the weight of 1 cubic foot of steam at 7 
pounds absolute is .0189 pounds and the total weight of 
steam exhausted per minute would be 1,974.4 X .0189 = 
37.3 pounds, and if 18.65 pounds of water is required to 
condense 1 pound weight of steam at 7 pounds absolute, 
the total weight of water required per minute in this case 
would be expressed as follows: 37.3 X 18.65 = 695.8 
pounds, or per hour 695.8 X 60 = 41,748 pounds, equal to 
5,029 gallons. 

Ques. 589. — What quantity of condensing water would 
be required in a surface condenser, assuming the condi- 
tions to be the same as described in the answer to question 
587? 

Ans. — A surface condenser requires about 15 to 
20 per cent more condensing water than a jet condenser 
does. It was seen in the answer referred to that 18.65 
pounds of water were required to condense 1 pound 
weight of steam, therefore the quantity of water required 
by the surface condenser would be about 22 or 23 pounds 
for each pound of steam. 

Ques. 590. — What provision is made on board of 
vessels for obtaining a supply of water for the condensers 
and for other purposes? 



CONDENSERS — AIR-PUMPS — SEA-WATER 



237 



Table io 
Areas and Circumferences of Circles. 



Diam. 


Area. 


Circum. 


Diam. 


Area. 


Circum. 


Diam. 


Area. 


Circum, 


.25 


.049 


.7854 


15.5 


188.692 


48.694 


31 


754.769 


97.389 


.5 


.1963 


1.5708 


16 


201.062 


50.265 


31.25 


766.992 


98.175 


I.O 


.7854 


3.1416 


16.25 


207.394 


51.051 


31.5 


799.313 


98.9b8 


1.25 


1. 2271 


3.9270 


16.5 


213.825 


51.836 


32 


804.249 


100.53 


1.5 


I.7671 


4.7124 


17 


226.980 


53^407 


32.25 


816.86 


101.31 


2 


3.1416 


6.2832 


17.25 


233.705 


54. 192 


33 


855.30 


103.67 


2.25 


3.9760 


7.0686 


17.5 


240.520 


54.978 


33.25 


868.30 


104.45 


2.5 


4.9087 


7.8540 


18 


254.469 


56.548 


33.5 


881.41 


105.24 


3 


7.0686 


Q.4248 


18.25 


261.587 


57.334 


34 


907.92 


106.81 


3.25 


8.2957 


10.210 


18.5 


268.803 


58.119 


34.25 


921.32 


107.60 


3.5 


9.6211 


10.995 


19 


283.529 


59.690 


34.5 


934.82 


108.38 


4 


12.566 


12.566 


19.25 


291.039 


60.475 


35 


962.11 


106.95 


4.25 


14.186 


13.351 


19.5 


298.648 


61.261 


35.25 


975.90 


110.74 


4.5 


15.904 


14.137 


20 


314.160 


62.832 


35.5 


989.80 


III. 52 


5 


19.635 


15.708 


20.25 


322.063 


63.617 


36 


IO17.8 


113.09 


5.25 


21.647 


16.493 


20.5 


330.064 


64.402 


36.25 


1032.06 


113.88 


5.5 


23.758 


17.278 


21 


346.361 


65.973 


36.5 


1046.35 


114.66 


6 


28.274 


18.849 


21.25 


354.657 


66.759 


37 


1075.21 


116.23 


6.25 


30.679 


19.635 


21.5 


363.051 


67.544 


37.25 


1089.79 


117.01 


6.5 


33.183 


20.420 


22 


380.133 


69.115 


37.5 


1104.46 


117.81 


7 


38.484 


21.991 


22.25 


388.822 


69.900 


38 


II34.II 


119.38 


7.25 


41.282 


22.776 


22.5 


397.608 


70.686 


38.25 


1149.08 


120.16 


7.5 


44.178 


23.562 


23 


415.476 


72.256 


38.5 


I164.15 


120.95 


8 


50.265 


25.132 


23.25 


424.557 


73.042 


39 


if94.59 


122.52 


8.25 


53.456 


25.918 


23.5 


433.731 


73.827 


39.25 


1209.95 


123.30 


8.5 


56.745 


26.703 


24 


452.390 


75.398 


39.5 


1225.42 


124.09 


9 


63.617 


28.274 


24.25 


461.864 


76.183 


40 


1256.64 


125.66 


9.25 


67.200 


29.059 


24.5 


471.436 


76.969 


40.25 


1272.39 


126.44 


9-5 


70.882 


29.845 


25 


490.875 


78.540 


40.5 


1288.25 


127.23 


10 


78.540 


31.416 


25.25 


500.741 


79.325 


41 


1320.25 


128.80 


10.25 


82.516 


32.201 


25.5 


510.706 


80.110 


41.25 


1336.40 


129.59 


10.5 


86.590 


32.986 


26 


530.930 


81.681 


41.5 


1352.65 


130.37 


II 


95.033 


34.557 


26.25 


541.189 


82.467 


42 


1385.44 


131.94 


11.25 


99.402 


35.343 


26.5 


551.547 


83.252 


42.25 


1401.98 


132.73 


11.5 


103.869 


36.128 


27 


572.556 


84.823 


42.5 


1418.62 


133.51 


12 


113.097 


37.699 


27.25 


583.208 


85.608 


43 


1452.20 


135.08 


12.25 


117.859 


38.484 


27.5 


593.958 


86.394 


43.25 


1469.13 


135.87 


12.5 


122.718 


39.270 


28 


615.753 


87.964 


43.5 


1486.17 


136.65 


13 


132.732 


40. 840 


28.25 


626.798 


88.750 


44 


1520.53 


138.23 


13.25 


137.886 


41.626 


28.5 


637.941 


89.535 


44.25 


1537.86 


139.01 


13.5 


143. 130 


42.411 


29 


660.521 


91.106 


44.5 


1555.28 


139.80. 


14 


153.938 


43.982 


29.25 


671.958 


91.891 


45 


1590.43 


141.37 


14.25 


159.485 


44.767 


29.5 


683.494 


92.677 


45.25 


1608.15 


142.15 


14.5 


165.130 


45.553 


30 


706.860 


94.248 


45.5 


1625.97 


142.94 


15 


176.715 


47.124 


30.25 


718.690 


95.033 


46 


1661.90 


144.51 


15 25 


182.654 


47.909 


30.5 


730.618 


95.818 


46.25 


1680.01 


145.29 



238 



QUESTION^ AND ANSWERS 



Table io—Cona?iued, 



Diam. 


Area. 


Circum. 


Diam. 


/ lea. I Circum. 


Diam. 


Area. 


Circum. 


46.5 


1698.23 


146.08 


62.25 


3043.47 


195.56 


78 


4778.37 


245.04 


47 


1734. 9A 


147.65 


62.5 


3067.96 


196.35 


78.25 


4809.05 


245.83 


47.25 


1753.^5 


148.44 


63 


3117.25 


197.92 


78.5 


4839.83 


246.61 


47.5 


1772.05 


149.22 


63.25 


3142.04 


198.71 


79 


4901.68 


248.19 


48 


1809.56 


150.79 


63.5 


3166.92 


199.50 


79-25 


4932.75 


248.97 


48.25 


1828.46 


151.58 


64 


3216.99 


201.06 


79.5 


4963.92 


249. 76 


48.5 


1847.45 


152.36 


64.25 


3242.17 


201.85 


80 


5026.56 


251.33 


49 


1885.74 


153.93 


64.5 


3267.46 


202.68 


80.5 


5089.58 


252.90 


49-25 


1905.03 


154.72 


65 


3318.31 


204.20 


81 


5153.00 


254.47 


49-5 


1924.42 


155.50 


65.25 


3343.88 


204.99 


81.5 


5216.82 


256.04 


50 


1963.50 


157.08 


65.5 


3369.56 


205.77 


82 


5281.02 


257.61 


50.25 


1983.18 


157.86 


66 


3421.20 


207.34 


82.5 


5345.62 


259.18 


50.5 


2002.96 


158.65 


66.25 


3447.16 


208.13 


83 


5410.62 


260. 75 


51 


2042.82 


160.22 


66.5 


3473.23 


208.91 


83.5 


5476.00 


262.32 


51.25 


2062.90 


161.00 


67 


3525.66 


210.49 


84 


5541.78 


263.89 


51.5 


2083.07 


161.79 


67.25 


3552.01 


211.27 


84.5 


5607.95 


265.46 


52 


2123.72 


163.36 


67.5 


3578.47 


212.06 


85 


5674.51 


267.04 


52.25 


2144.19 


164.14 


68 


3631.68 


213.63 


85.5 


5741.47 


268.60 


52.5 


2164.75 


164.19 


68.25 


3658.44 


214.41 


86 


5808.81 


270.17 


53 


2206.18 


166.50 


68.5 


3685.29 


215.20 


86.5 


5876.55 


271.75 


53.25 


2227.05 


167.29 


69 


3739-28 


216.77 


87 


5944.66 


273.32 


53.5 


2248.01 


168.07 


69.25 


3766.43 


217.55 


87.5 


6013.21 


274.89 


54 


2290.22 


169.64 


69.5 


3793.67 


21S.34 


88 


6082.13 


276.46 


54.25 


2311.48 


170.43 


70 


3S48.46 


219.91 


88.5 


6151.44 


278.03 


54.5 


2332.83 


171. 21 


70.25 


3875.99 


220.70 


89 


6221.15 


279.60 


55 


2375.83 


172.78 


70.5 


3903.63 


221.48 


89.5 


6291.25 


281.17 


55.25 


2397.48 


173.57 


71 


3959-20 


223.05 


90 


6371.64 


282.74 


55.5 


2419.22 


174.35 


71.25 


3987.13 


223.84 


90.5 


6432.62 


284.31 


56 


2463.01 


175.92 


71.5 


4015.16 


224.62 


91 


6503.89 


285.88 


56.25 


2485.05 


176.71 


72 


4071.51 


226.19 


91.5 


6573.56 


287.46 


56.5 


2507.19 


177.5 


72.25 


4099.83 


226.98 


92 


6647.62 


289.03 


57 


2551.76 


179.07 


72.5 


4128.25 


227.75 


92.5 


6720.07 


290.60 


57.25 


2574.19 


179.85 


73 


41S5.39 


229.34 


93 


6792.92 


292.17 


57.5 


2596.72 


180.64 


73.25 


4214.11 


230.12 


93.5 


6866.16 


293.74 


58 


2642.08 


182.21 


73.5 


4242.92 


230.91 


94 


6939-79 


295.31 


58.25 


2664.91 


182.99 


74 


4300.85 


232.48 


94.5 


7013.81 


296.88 


58.5 


2687.83 


183.78 


74.26 


4329.95 


233.26 


95 


7088.23 


298.45 


59 


2733.97 


185.35 


74.5 


4359.16 


234.05 


95.5 


7163.04 


300.02 


59.25 


2757.19 


186.14 


75 


4417.87 


235.62 


96 


7238.25 


301.59 


59.5 


2780.51 


1S6.92 


75.25 


4447.37 


236.40 


96.5 


7313-80 


303.16 


60 


2827.44 


188.49 


75.5 


4476.97 


237.19 


97 


7389.81 


304.73 


60,25 


2851.05 


189.28 


76 


4536.37 


238.76 


97.5 


7466.22 


306.30 


60.5 


2874.76 


190.06 


,76.25 


4566.36 


239-55 


98 


7542.89 


307.88 


61 


2922.47 


191,64 


76.5 


4596.35 


240.33 


98.5 


7620.09 


309.44 


61.25 


2946.47 


192.42 


77 


4656.63 


241.90 


99 


7697.70 


311.02 


61.5 


2970.57 


193.21 


77 25 


4686.92 


242.69 


99.5 


7775.63 


312.58 


62 


3019.07 


194.78 


77.5 


4717.30 


243.47 


100 


7854.00 


314.16 



CONDENSERS AIR-PUMPS SEA-WATER 



239 



Ans. — All holes in the hull of a ship below the water- 
line for the supply or discharge of condensing wa- 
ter, or for any other purpose, are fitted with valves 
having long spindles 
which are brought inside 
the vessel through stuff- 
ing boxes, in order that 
the valves may be worked 
from inboard. The cir- 
culating pumps take 
their suction from a 
large screw-down inlet 
valve on the bottom of 
the ship, while the dis- 
charge is through simi- 
lar valves on the ship's 
side. 

Ques. 591.— What 
type of valve is largely 
used for this purpose? 

Ans. — The Kingston 
sea-valve. Strainers are 
placed over all inlets, to 
prevent the entrance of 
weeds and other impuri- 
tieSc 

Fig. 157. Sea-vai^ve. 




CHAPTER VIII 

AUXILIARY MACHINERY AND FITTINGS 

Ques. 592. — Besides the air and circulating pumps, 
what other pumps are required in well-equipped steam 
plants, or aboard steam-ships? 

Ans. — Boiler feed-pumps, fire -service, pumps for 
hydraulic elevators, and other service requiring water- 
pressure, and in addition, on ship-board, pumps are 
required for emptying the bilges and tanks and for supply- 
ing water for washing the decks, evaporator service and 
for sanitary purposes. 

Ques. 593. — Is there a special pump provided for each 
seivice? 

Ans. — Not in all cases, but one pump may be con- 
nected in such a manner as will permit of its being used 
alternately for several different purposes. However, a 
special pump is, or at least should always be provided for 
feeding the boilers. Also a special bilge-pump is usually 
supplied, for the reason that it handles very dirty water, 
that should not be passed through any other pipe system. 
In small vessels one pump (the donkey) usually serves for 
nearly all purposes, including auxiliary boiler-feed, and 
on Western river steamers an independent pump (the 
doctor) having a steam-cylinder and walking-beam, drives 
a system of pumps for feed, fire and bilge-pumping 
service. 

240 



AUXILIARY MACHINERY AND FITTINGS 



241 



Ques. 594. — What special features should appertain 
to the boiler feed-pump? 

Ans. — It should be simple, durable, of great strength 
and ample capacity to insure regular and reliable service 
under the most severe conditions. It is always best to 
have the main and auxiliary feed-pumps duplicates of 
each other if possible, for the reason that in cases of 

emergency the different 
parts are interchangeable. 
In the marine service the 
main feed-pump draws its 
supply of water from the 
hot well, feed-heater or the 
feed-tank, as the case may 
be. The auxiliary or du- 
plicate feed-pump may be 
arranged so as to draw 
from either of these sources, 
and also from the sea, thus 
making provision for 
emergency. 

Ques. 595. — W here 
should the feed-pumps be 
located? 

Ans. — As near to the boiler-room as possible, in order 
that the engineer in charge of the boilers may have full 
control of the feed-water supply. On board of vessels^ 
when the feed-pump is worked from the main engine, the 
auxiliary, or injector is usually placed in the stoke-hold. 
Ques. 596,— What type of boiler feed-pump has 




Fig. 158- The Worthington Boiler- 
feed Pump, Admiralty Pattern. 
For 250 Pounds Pressure. 



242 QUESTIONS AND ANSWERS 

been found to be the most reliable for all kinds of 
service? 

Ans. — The double acting steam-pump, working inde^ 
pendently of all other machinery. The horizontal variety 
is principally used for land service, while on board steam 
vessels the vertical type is preferred, for the reason that 
it occupies less floor space. In both the horizontal and 
vertical types, the water valve-chambers have removable 
covers, allowing a ready access to the valves and valve- 
seats. The steam-valves of these pumps are actuated in 
various ways. In the duplex variety, which consists of 
two pumps combined into one, the steam-valve of one 
side is moved from the piston-rod of the other, and vice 
versa, while with a pump having but a single steam-cylin- 
der, the steam-valve is worked by a tappet action from 
.ts own piston-rod. 

Ques. 597. — What two varieties of feed-pumps are 
largely in use on ocean steamers? 

Ans. — The Weir vertical double-acting steam-pump 
and the Belleville, which is built either vertical or horizon- 
tal. In the Weir pump the water-valves are a series of 
small cones milled out of solid metal and give a large 
area of opening with a slight lift. The steam-valve 
arrangement of the Weir pump is rather complicated and 
requires to be maintained in perfect condition, to insure 
good service. It consists of a main valve for distributing 
steam to the cylinder and an auxiHary valve for distribu- 
ting steam to work the main valve. The main valve moves 
horizontally from side to side, being driven bv >si:/»-«« 
admitted and exhausted from each end alternatelv. The 



AUXILIARY MACHINERY AND FITTINGS 



243^ 



auxiHary valve is actuated by a lever with a fixed fulcrum 
worked by the piston- 
rod of the pump. This 
auxiliary valve moves on 
a flat face on the back of 
the main valve and in a 
direction at right angles 
to the latter. Both the 
main and auxiliary valves 
are simply slide valves, 
but the main valve is half 
round, the round side 
working on the corre- 
spondingly shaped cylin- 
der port-seat, while the 
back of the valve is flat 
and forms the seat for 
the auxiliary valve. Both 
ends of the main valve 
are lengthened, so as to 
project beyond the port 
face and are turned cylin- 
drical, with flat ends. 
Caps are fitted on each 
of these ends, forming 
cylinders which are 
closed at the mouths by 
the flat ends of the main 
valve, which act as pis- 

tons, the length of stroke Marine Service. 




244 QUESTIONS AND ANSWERS 

that the piston can make being the full travel of the 
valve. The auxiliary valve-seat has three ports, the 
center one being the exhaust and the two side ports being 
steam-passages leading through the piston ends of the 
main valve. The right-hand cylinder port-passage is led 
through the left-hand end of the piston and the left-hand 
passage leads to the other end. These ports admit steam 
to the two small caps or cylinders at each end of the valve 
alternately, by which it is thrown from side to side. 
Besides the ports already referred to, there are two 
other ports formed on the auxiliary valve-seat leading to 
and corresponding to two ports on the half-roimd seat of 
the main valve. These ports are for the purpose of 
admitting steam to the top and bottom of the main cylin- 
der, and are arranged on the auxiliary valve-seat to cut 
off steam before the end of the stroke, and so reduce the 
speed of the piston, but the expansion chambers at each 
end of the main valve are fitted with by-passes to admit 
steam for the full stroke when so desired. This may be 
necessary when starting the pump, as then the water- 
cylinder may be full of water. These by-passes are formed 
by notches cut in the edges of the caps and may be opeied 
or closed by turning the caps by means of spindles pro- 
vided at each side of the valve-chest, and thus give a 
definite cut-off. There are separate by-passes for the up 
and down strokes, and the silent working of the pump 
depends upon the proper adjustment of these by-passes. 

Ques. 598. — Describe the action of the Belleville feed- 
pump. 

Ans. — The pump is double-acting, having an ordinary 



AUXILIARY MACHINERY AND FITTINGS 



245 



flat slide-valve without lap, worked by a curved lever, 
which is moved at each end of the stroke, by a projection or 
lug on the piston-rod. The steam-ports are arranged at 
each end of the cyh'nder in such a manner as to admit the 
steam uniformly all around the cylinder circumference, 
and not at the top only, which prevents bending forces 
on the rod. The steam-pressure remains constant, 
therefore, until near the end of the stroke, when the pro- 
jection strikes the valve-lever and commences to close the 



LONGITUDINAL SECTION 




Fig. 160. Bei^levili^e Feed-pump. 



steam-valve, so that the steam-pressure falls and the 
motion would cease, but for special provisions. Before 
the piston can commence the return stroke, it is necessary 
that the valve should not only be closed but pushed suffi- 
ciently far over to reopen for steam on the other side. 
To enable the steam already in the cylinder to complete 
the stroke and throw the valve over to the opposite side, 
an orifice is provided at each end of the water-cylinder, 
closed by levers and communicating with the suction- 
chamber, so that when the water-piston nears the end of 



246 



QUESTIONS AND ANSWERS 



its stroke, it strikes one of these levers and opens the orifice 
to the suction-chamber, thus causing the pressure in the 
water-cylinder to fall, and the steam, although cut oflf, 
is enabled by its expansive force to push the piston to the 
end of the stroke and reverse the valve. When motion 
begins in the opposite direction the water-valves are a 
series of small valves, generally eight in number, at each 
end, four for suction and four for discharge. Small holes 
about tV inch in diameter, are made through the levers into 



mo mier - ) ^ 





F££D^ W/TLiT 



v^/wu/z/^i<^m/uur///i//w////^ 



Fig. 161. Kirkaldy's Feed-heater. 




sT£A§t oome^ 



the passage leading to the suction chamber, so that a 
small quantity of water is always escaping from the water- 
cylinder, which causes the pump to keep slowly in motion, 
even when the feed-valves on the boilers are closed. 

Ques. 599. — Are feed-water heaters much in use in 
the marine service? 

Ans. — They are largely used in the mercantile service, 
and results justify their adoption. 

Ques. 600. — Describe the construetion and operation 
of Kirkaldy's feed-heater. 



AUXILIARY MACHINERY AND FITTINGS 



247 



Ans. — It is constructed along lines similiar to a sur- 
face condenser, having tubes rolled into tube-plates in the 
ordinary manner, the whole surrounded by an outside shell, 
leaving spaces at each end between the tube-plates and 
end-covers. The feed-water does not mix with the 
heating steam, but is drawn through the tubes, on thcj 




Fig. 162. Weir's Fekd-heater and Regulator. 



outside of which is the steam, which is usually the exhaust 
from various auxiliary engines, or it may be drawn from 
the boilers. By-pass valves are fitted, so that when 
necessary the feed-water can be passed direct, without 
passing through the heater. 



248 



QUESTIONS AND ANSWERS 



Ques. 601. — Describe the construction and operation 
of Weir's feed-heater and regulator. 

Ans. — It takes steam from the final receiver of the 
engine after it has done most of its work. The steam 
enters the heating chamber through a circular perforated 
ring and there mixes with the cold feed-water, which is 
admitted through the spring-loaded valve on the cover. 




Fig. 163. The Harris Grease Fii^ter. 

The heated water falls to the bottom of the heaterj from 
whence it is removed by the feed-pump. A galvanized 
iron float is fitted to the bottom of the heater, which 
communicates by means of levers with the steam-valve 
leading to the feed-pump, thus keeping the water-level 
constant in the heater and preventing the pumps from 
drawing; air. 



» AUXILIARY MACHINERY AND FITTINGS 249 

Ques. 602. — What provision is made ori board steani' 
vessels for the prevention of oil or grease passing into 
the boilers along with the feed-water? 

Ans. — Numerous types of grease-filters are in use. 
In the Harris grease-filter the feed-water is caused to pass 
through a series of gratings, on each of which is fitted 
one or two sheets of filtering material, consisting of 
toweling or flannel, supported by wire gauze. When the 
cloths become dirty they are cleaned by a steam jet, and 
washed off by a reverse current of water. 

Ques. 603. — What is the object of placing a governor 
on an engine? 

Ans. — To maintain regularity of speed of the engine 
when the load is varied from any cause. 

Ques. 604. — -Upon what principle do the most of the 
governors for land engines operate? 

Ans. — Upon the principle of centrifugal force causing 
two balls or weights, each suspended or attached to a lever 
swinging on a fulcrum, fixed near the top of a vertical 
revolving spindle, to fly outward as the speed increases; 
and the force of gravitation which acts in the opposite 
direction as the speed decreases. The outward movement 
of the balls or weights is utilized to either close the throt- 
tle or shorten the point of cut-off, while the inward move- 
ment has the opposite effect. 

Ques. 605. — Are governors required on marine en- 
gines? 

Ans. — They are, for the reason that in a marine engine 
considerable diminution in resistance may ensue in rough 
or stormy weather, from the pitching motion of the vessel, 



250 QUESTIONS AND ANSWERS 

which causes the propellers to rise partly out of the water, 
thus causing what is technically known as *"racing of 
the engines/' 

Ques. 606. — Is the centrifugal type of governor suit- 
able for marine service? 

Ans. — It is not, for the reason that the forces acting 
upon the balls or weights would be affected by the motion 
of the ship and the action would be irregular. Other 
forms of governors for marine engines are in use with 
various degrees of success, but all, or nearly all of them, 
possess the one defect of requiring an increased speed of 
the engine to cause them to act, and even then their action 
is sluggish, the throttle-valve being generally closed after 
the racing is over. 

Ques. 607. — What type of marine governor is likely 
to prove the most successful in marine service for the 
prevention of **racing?" 

Ans. — A governor that acts by variations of pressure 
at the stern of the vessel near the propeller, and not 
from engine-speed variations. Racing being caused by 
diminished immersion of the propeller, it is accompanied 
by a diminution of pressure of water at that part, which 
can be utilized to actuate the throttle-valve. Such gov- 
ernors may therefore anticipate and prevent any increase 
of speed due to the above cause, although they would have 
no effect in case of a serious increase of speed, due to 
such an accident as a broken shaft or propeller. 

Ques. 608. — Describe Dunlop's governor, which is of 
the latter type. 

Ans. — It consists of a sea-cock at the stern of the 



AUXILIARY MACHINERY AND FITTINGS 251 

ship, opening into an air-vessel or air-chamber, so con- 
structed that, by opening the sea-cock, water flows into 
the air-vessel and compresses the air contained therein to 
a pressure equivalent to the head of water outside the 
ship. From the top of the air-chamber a pipe is led to 
the under side of an air-tight elastic diaphragm, forming 
part of an apparatus in the engine-room. On the upper 
side of the diaphragm is a spiral spring, with means of 
adjusting its compression to balance the air pressure 
below the diaphragm. From the center of the diaphragm 
a connection is made to the slide-valve of a small steam- 
cylinder so constructed that its piston moves in exact 
accordance with the movements of the diaphragm. This 
steam-piston is connected by suitable gear to the throttle- 
valve of the engine whose speed is to be controlled. The 
action is as follows: The sea-cock being open, any varia- 
tion of head of water outside the ship is accompanied by 
an inflow or outflow of water through it and consequently 
a variation in the pressure of the air contained in the air- 
chamber, and also under the diaphragm of the engine-room 
apparatus, causing the diaphragm to move through such 
part of its travel as is requisite to enable the compression 
of spring and the air-pressure to balance each other again. 
Every movement of the diaphragm is followed by a 
corresponding movement of the governor steam-piston, 
and consequently of the throttle-valve of the engines 
under control, the time taken between the variation in 
the head of water at the stern of the ship and the moving 
of the throttle-valve being practically nothing. The 
governor therefore anticipates any increase in the speed 



252 



QUESTIONS AND ANSWERS 



of the engines due to the propeller rising out of the water 

and does not depend upon a variation in speed of the 
engines to be controlled, before it acts. By adjusting the 
balance between the spring and the air-pressure under the 
diaphragm the diaphragm begins to fall and the throttle- 
valve to close, when the tips of the propeller-blades rise 



B 

P/P£L£0 TO 
C THE BOTTOtt 
OF A/R-TJCMT 
D/APH/fA6M 




Sea CocKFjrrEo //E/ts 



Fig. 164. Bunlop's Governor. 

to any desired distance above the surface of the water. 
The air-vessel should be fitted as far aft in the screw-tun- 
nel as possible, the hole through the side of the vessel 
being placed about one-fourth the diameter of the 
propeller below the level of the center of the shaft. The 
reports of the action of this governor in the mercantile 



AUXILIARY MACHINERY AND FITTINGS 



253 



marine are very satisfactory. It is fitted in the ''Cam- 
pania/' '*Paris/' and many other vessels. 

Ques. 609. — How is the fresh water needed on board 
ship for drinking, washing, culinary purposes, and for 
making up for the waste of feed-water for the boilers and 
for various other purposes, obtained? 




Normandy's Evaporator. 



Ans, — By means of evaporators and distillers. The 
evaporators are really small boilers, with heat obtained 
from steam passing through tubes, while the water to be 
evaporated surrounds the tubes. There is no coal used 
in these boilers, the steam being obtained from the main 



254 QUESTIONS AND ANSWERS 

boilerSc The vapor produced is conducted to the distilling 
apparatus, where it is condensed into fresh drinking 
water, and a portion of it goes to the condensers for the 
purpose of making up the deficiency of boiler feed-water. 
The condensed primary steam is returned to the boilers. 

Ques. 610. — Describe Normandy's evaporator. 

Ans. — In this type of evaporator the tubes are all 
straight and rolled into tube-plates at their ends. The 
steam from the main boilers enters these tubes through a 
pipe at the top and evaporates the surrounding sea-water 
contained in the shell, and is itself condensed and passes 
out through the bottom, returning to the boilers. The 
vapor generated outside the tubes is conveyed by a valve 
and pipe, either to the auxiliary condenser for feed-water 
make-up, or else to the distilling condensers for the 
production of drinking water. The resulting scale is 
deposited in the evaporator, from whence it is cleaned at 
intervals. The sea-water for the evaporator is supplied 
by a pump. It takes its supply from a feed-box contain- 
ing a float which maintains a constant level in the feed- 
box. 

Ques. 611. — Describe Normandy's condenser. 

Ans. — The steam from the evaporator enters the con- 
denser through a pipe at the top and passes downwards 
through two series of tubes, the upper set being the 
condensing and the lower the cooling tubes. These tubes 
are surrounded by a casing, which is kept filled with cold 
iSea-water that enters at the bottom and flows out at the 
top through an overflow pipe that is connected to the 
casing at a point a short distance below the top and is 



AUXILIARY MACHINERY AND FITTINGS 255 

then carried to some distance above the top of the cham- 
ber before discharging overboard. By means of this 
arrangement the hottest sea-water is not discharged over- 
board, but instead may be used in the evaporator, in 
connection with the condenser, and thus promote economy 
of evaporation. An air-pipe is fitted to allow the air 
evolved from the condensing water in the casing by heat 
to pass into the overflow pipe leading to the sea. The 
condensed water rises from the lower chamber through a 
stand-pipe connected at the bottom and overflows from 
this pipe into and down another pipe leading to the suction 
of a small steam donkey pump, which pumps it into test- 
tanks, from whence it flows by gravity to the water-tanks 
in the hold of the vessel. By this arrangement the cool- 
ing tubes of the condenser are always kept full of water 
and the fresh water is drawn oflf cold. 

Ques. 612. — On vessels carrying cargoes of fresh 
meat and other perishable articles that are affected by 
the heat, what provision is made for their preservation? 

Ans. — Various types of refrigerating machinery are in 
use, some using the cold-air system, others the carbonic- 
acid system, and a few of the smaller ships are fitted with 
machines for making ice only. 

Ques. 613. — Describe the cold-air system. 

Ans. — The machine consists of a tandem compound 
engine having piston slide-valves both on the same valve- 
rod and worked by a single eccentric. This engine 
supplies the motive power of the apparatus. Two air- 
cylinders, one called the compressing cylinder and the other 
one the expanding cylinder, are placed side by side and in 



256 QUESTIONS AND ANSWERS 

line with the low-pressure cylinder of the engine. These 
air-cylinders are double acting, the pistons receiving their 
motion from the crank-shaft driven by the engine. The 
action of the device is simple and is as follows: The 
revolving shaft, through the medium of connecting rods 
and guides, moves the pistons up and down. Air is 
drawn into the compressing cylinder through inlet-valves 
from the surrounding atmosphere or from the cold room. 
It is compressed on the return stroke of the piston and 
passes into the cooling chamber, which is constructed 
similar to a surface condenser, having a pump to circu^ 
late the cooling sea-water through it. The work done thus 
far appears as heat in the air and this heated air, passing 
through the tubes of the air-cooler, is cooled by the cir- 
culating water and is then led to the valve-chamber of the 
expanding cylinder. The valve arrangement of this 
cylinder consists of a slide-valve and an expansion valve 
working on the back of the slide-valve. This arrange- 
ment supplies a means of sharply cutting off the inlet of 
air when it enters the expanding cylinder. The compress- 
ing cylinder is provided with a water-jacket through 
which the circulating pump delivers the cooling water on 
its way from the air-cooler to the sea. The slide-valves 
are so arranged in the expanding cylinder that when the 
proper quantity of air is admitted the supply is cut off 
and during the remainder of the stroke the air expands 
and therefore does work on the piston and heat is 
expended in the process in exactly the converse manner 
to the generation of heat in the compressing cylinder. 
As, however, the air has been deprived of its surolus heat 



AUXILIARY MACHINERY AND FITTINGS 



Z51 




Fic 165. CoLD-^iB System of Refrigeratiok. 



258 



QUESTIONS AND ANSWERS 



in the c(X)ling chamber, the heat eats^valent of the work it 
does in the expanding cylinder is absorbed from itself and 
the result is a considerable lowering of its temperature. 
This cold air is then exhausted through the orifice of the 
slide-valve in the usual manner, and conducted first to the 




Fig. 166. Carbonic-Acid System of Refrigeration. 

**snow-box'' a small accessible chamber in which the snow 
formed from the moisture is deposited, and from thence to 
the cold chamber, in which the supply of meat or provi- 
sions is kept and where it displaces air of a higher tem- 
perature. The refrigerating chamber is insulated by 
lagging its bulkheads, ceiling, and floor with silicate cottu^ 



AUXILIARY MACHINERY AND FITTINGS 259 

Dr other non-conductor, a teak lining being fitted o^er 

this to form the inside surface. 

Ques. 614. — Describe the carbonic-acid system. 

Ans. — A very successful and efficient device is the 
carbonic-anhydride system of Messrs. J. & E. Hall, in 
which carbonic anhydride is passed round continually in 
the circuit. The apparatus consists of three parts: a 
compressor, a condenser, and an evaporator. The com- 
pressor draws in heated and expanded gas from the 
evaporator and compresses it. The compressed gas then 
passes to a condenser, consisting of coils in which the 
warm compressed gas is cooled and liquefied by reduction 
of temperature caused by the action of the cooling sea- 
water. From the condenser the cool liquid carbonic 
anhydride is conveyed into the evaporator consisting of 
coils, where it vaporizes and expands, absorbing heat in 
the process and cooling the surrounding brine, which is 
in contact with the coils. This cold brine is circulated 
by a small pump to the refrigerating chamber, where it 
is conducted through a long series of rows of cooling 
pipes, termed **grids," which are placed at the roof of 
the chamber. The cold-brine **grids'* in this position set 
up a circulation of air, the cold air descending and being 
replaced by air not so cold, v/hich is cooled in its turn. 
Any moisture in the air is condensed on the **grids'' and 
appears as frost on the pipes. The theory of the action 
of this system is as follows : Under atmospheric pressure 
the liquid COg would evaporate at a temperature of 
120 degrees Fahrenheit below zero, but its temperature of 
evaporation rises with the pressure, in a similar manner as 



360 QUESTIONS AND ANSWERS 

water. At a pressure of 500 pounds per square inch it 
boils at a temperature of 30 degrees Fahrenheit so that 
cold water may be used to suppl}^ the heat for boiling it. 
The pressure in the evaporator is therefore regulated to 
the required temperature of the cooling water, so that a 
considerable pressure is necessary in the evaporator. The 
compressor draws the gas from the evaporator and com- 
presses it to the liquefying pressure, the heat due to the 
compression being absorbed by the cooling water in the 
condenser coils and the gas in .these coils becomes liquid 
before its exit. The liquid is then boiled in the evapora- 
tor coils, cooling the surrounding brine by the heat 
absorbed during evaporation. The compressor gland is 
made tight by cupped leathers with glycerine forced 
between them at a higher pressure than that in the com- 
pressor, so that no escape of gas can take place. The 
carbonic anhydride is supplied in steel cylinders to 
replenish the supply. 

Ques. 615. — What types of dynamos are used on board 
ships for generating electric current for internal illumi- 
nation and for working search-lights and motors? 

Ans. — They are usually of the two-pole type, direct 
driven and carried on an extension of the engine-bed. 
They have drum armatures and the field-magnets are 
compound wound, to give a constant pressure of 80 or 
100 volts for any current from zero to the maximum, 
while the speed is maintained constant. The usual speed 
is 320 revolutions per minute. The machines are con- 
nected to a switchboard located in a central position, from 
which the current is distributed to the various circuits for 



AUXILIARY MACHINERY AND FITTINGS 



261 



lighting, motors, etc. This board is so arranged that a 
circuit can be quickly changed from one machine to 
another, but no circuit can receive current from two 




262 QUESTIONS AND ANSWERS 

machines at the same time. The most recently fitted 
dynamos for the marine service are of the iron-clad type, 
the field coils and the armature being almost entirely 
surrounded by iron, to reduce to a minimum the leak- 
age of magnetic lines of force which may affect com- 
passes or chronometers in the neighborhood. 

Ques. 616. — How are these dynamos usually driven? 

Ans. — By vertical two-cylinder engines, generally 
compounded, although in some ships, where the steam- 
pressure is low, the engines are simple. All parts are 
carefully balanced and a heavy fly-wheel is fitted on the 
engine-shaft, at the dynamo end, which conduces to steady 
running. The speed is regulated by an isochronal governor 
fitted on the shaft. 

Ques. 617. — Describe the construction of the arma- 
ture. 

Ans. — The armature-core is built up of thin disks of 
soft iron slipped over metal sleeves, which are keyed on 
the shaft. The disks are insulated from each other by 
thin sheets of asbestos paper, to prevent loss of energy 
and heating due to eddy currents, and are kept in place 
by clamping-plates and end-nuts. The conductors on the 
armature, which carry the current, are made up of copper 
wires, twisted together, and pressed to a rectangular 
section. They are insulated by a covering of varnished 
tape. Usually two lengths of bars are used. They are 
placed around the periphery of the armature, longitudi- 
nally, long and short bars alternating, their ends overhang- 
ing the core. All the ends at one end of the armature 
project the came distance. Projections are fitted into the 



AUXILIARY MACHINERY AND FITTINGS 363 

core at intervals, which drive the conductor-bars. These 
projections are insulated by mica slips. The bars are 
kept in place by bands of steel or bronze binding wire, 
tightly wound on and soldered. Mica strips are placed 
under the bands to prevent injury to the insulation of the 
bars. Each bar is connected at each end by bent copper 
strips to another bar almost diametrically opposite to it, 
so that the whole of the bars and end-connections form 
one closed circuit. The projecting end of each long bar 
is also connected to the nearest commutator segment, the 
number of segments being equal to the number of long 




Fig. 168. Armature 

bars. Two or more pairs of brushes bear on the commu- 
tator, to collect the current, so that any brush may be 
lifted off without interrupting the circuit. 

Ques. 618. — Describe the construction of the field- 
magnet coils. 

Ans. — The field-magnet winding consists of shunt and 
series coils wound on a frame which fits over the 
upper pole-piece. The shunt coils are of small 
wire and high resistance. The ends of the wire 
are connected to the machine terminals. The greater 
part of the magnetism is due to these coils, so that at full 
speed, and when no current is being taken from the 



264 



QUESTIONS AND ANSWERS 



machine, the electric pressure is normal, that is, 80 or 
100 volts. The series coils are formed of thick copper 
bars and convey the whole current generated. They 
provide additional magnetism, proportional to the current 
flowing in them, and so compensate for the additional 




Fig. 169. Compound Wound Dynamo. 

pressure required to force this current through the 
machine. By the combination of the two sets of coils, the 
pressure is thus independent of the current, so long as the 
speed is constant. In the largest machines there are two 
distinct armature windings laid on side by side, the bars 



AUXILIARY MACHINER-i^ AND FITTINGS 265 

of the two Windings alternating, as also do their respec- 
tive commutator segments. The two windings are con- 
nected in parallel by the brushes, which all have a bearing 
rather wider than the angular width of two commutator 
segments. 

Oues. 619. — In order to obtain satisfactory working, 
what should be done with the comimutator occasionally? 

Ans. — It should be turned up, by using a lathe slide- 
rest clamped to the bed-plate and running the engines as 
slowly as possible, and after turning, the commutator 
should be polished. This truing up is necessary in order 
to remove any flat places which are liable to form on the 
segments. The brushes also should be carefully filed to 
fit the commutator curve. The brushes must be care- 
fully set in the holders, with all the tips of each set in a 
line, and the tips of the two sets bearing simultaneously 
on diametrically opposite commutator segments. Gener- 
ally two segments are marked at their ends, with crosses, 
to assist in this adjustment. 

Ques. 620. — How is the electric current carried to the 
different parts of the ship? 

Ans. — By wires of the best copper, thoroughly insu- 
lated and protected from injury by being placed in wooden 
mouldings, or what is still better, iron tubes lined with 
insulating material. The junction boxes have safety 
fuses and connections, arranged in incombustible porce- 
lain or lava blocks. 

QueSo 621.-— How are the lamps and motors arranged? 

Ans. — ^The lamps are attached to substantial supports 
with good protection to the insulation of the wires at their 



366 QUESTIONS AND ANSWERS 

connection. For exposed places extra globes or wire 
screens are provided ft) prevent breaking of the bulbs. 
The motors are fitted on substantial foundations, with 
switches for handling in convenient positions. The use 
of electric motors is becoming more and more general on 
board vessels as their convenience and freedom from 
waste is known. They can be used for working ven* 
tilating fans, etc., in confined spaces where the heat of 
steam would be objectionable. They also avoid the waste 
due to condensation, radiation and leakage in pipes, 
require very little attention when running and are always 
ready for starting. 

Ques. 622. — What facilities are provided for pumping 
the water out of steam-ships in case of a serious leak? 

Ans. — All steam-ships, including war-vessels, were 
formerly fitted with bilge-pumps worked direct from the 
main engines, and this is still the common practice in the 
mercantile marine. In addition to these pumps, the 
circulating pumps are fitted with bilge as well as sea 
connections, and in some of the larger vessels there are 
four centrifugal pumps which can be used for pumping 
out the bilges, each of these pumps having a capacity of 
at least 1,200 tons of water per hour. 

Ques. 623. — What are some of the requirements of a 
reliable bilge-pumping outfit? 

Ans. — ^The pump itself should be close to the bilge, 
but the engine for working it should if possible be at a 
high level, so as to be out of the reach of the water in 
case of its rising rapidly. Another point that should be 
kept in view is the provision of large engine-power for 



AUXILIARY MACHINERY AND FITTINGS 



267 



working the pumps. The valves for changing the suction 
of the centrifugal pumps from the sea to the bilge are, or 
at least should be, arranged to be worked from the start- 
ing platform, and to enable this to be done quickly in 
case of need, the valves in the sea and bilge-suction pipes 





Fig. 170, Fire and Bilge Pumps. 



are often coupled together so that they may be worked 
by a single lever. 

Ques. 624. — Describe the type of fire and bilge-pump- 
ing engines that are used to a large extent in the English 
navy. 



268 QUESTIONS AND ANSWERS 

Ans. — Each pumping engine consists of two double- 
acting pumps and two steam-cylinders, fitted with 
slide-valves, having very little lap, to insure the engines 
starting readily from any position of the cranks, economy 
m the use of steam being in these cases a minor considera- 
tion. In the large battle-ships and cruisers there are four 
,of these pumps, two in each engine-room, each one of the 
four having a capacity of 80 to 120 tons of water per 
hour. The pumps are large enough to remove these 
quantities of water at a speed not exceeding 60 revolu- 
tions per minute, with a steam-pressure of two-thirds 
the maximum boiler-pressure, and they form a means of 
pumping water out of the ship, auxiliary to the main 
circulating pumps. They can be used for either fire ser- 
vice or for clearing the bilges of water. 

Ques. 625. — Describe Friedmann's bilge-ejector. 

Ans. — This apparatus is a modification of Giffard's 
injector, the number of nozzles being increased so as to 
give the steam several suction orifices instead of one. 
The steam is conducted to a tuyere about one-half the 
diameter of the steam-pipe, and then passes successively 
through a series of intermediate tuyeres, through which 
the water is drawn from the hold and expelled from the 
ship through the discharge. The device occupies little 
space and has considerable capacity, but its consumption 
of steam is large. 

Ques. 326. — Describe the suction and discharge 
arrangements of fire and bilge pumps. 

Ans.— They are fitted with separate suction-pipes 
leading: to the following parts of the vessel: Forward 



AUXILIARY MACHINERY AND FITTINGS 



269 



and after ends of engine-room, with a continuation to 
the screw tunnel from the latter, main engine save-all, 
each boiler compartment, the main suction-pipe, salvage 
system of the vessel and to the sea. The valve-boxes 
and pipes are so arranged that each pump can draw from 
any of these parts. The pumps deliver water either over- 
board direct, to the engine-room or to the fire-main, a 
large air-vessel being fitted in connection with the latter. 




JP/SCHARGK 79 
EN&INC AQCM" 



TO ATTJCft BMQINS tiOOM D 
* SCn£W rUNNCL — -. T5f 



r=»\ /otrweEff^ sverroN Boxts 




Fig. 171. Suction and Discharge Arrangements oe Fire and Bii,ge Pumps. 

A A A A, pumps; B B, directing valve-boxes; C C, shut-off valves from 
the sea, and bilge directing valve-box respectively: D D, directing valves for 
discharge, either to fire main, overboard or to engine-room. 

Ques. 627. — How is the fire-main arranged? 

Ans. — The fire-main is a pipe extending fore and aft 
in the ship, with branches leading to different parts as 
required. Delivery-valves, with screwed nozzles for hose- 
connections, are located at various points in the fire-main. 
Non-return valves are fitted at the junction of delivery- 
pipes from the pumping engines. 



CHAPTER IX 

THE INDICATOR — PRINCIPLES OF THE INDICATOR 

Ques. 628. — By whom was the indicator invented and 
first applied to the steam-engine? 




Fig. 172. Sectionai, View Crosby Indicator. 

Ans. — The indicator was invented and first applied to 
the steam-engine by James Watt, whose restless genius 

270 



THE INDICATOR PRINCIPLES OF INDICATOR 



371 



was not satisfied with a mere outside view of his engine 
as it was running, but he desired to know more about the 
action of the steam in the cylinder, its pressure at differ- 
ent portions of the stroke, the laws governing its expan- 
sion after being cut off, etc. Watt's indicator, although 
crude in its design and construction, contained embodied 
within it all of the principles of the modern instrument. 

Ques. 629. — What are the principles governing the 
action of the indicator? 

Ans. — First, the pressure of the 
steam in the engine-cylinder throughout 
an entire revolution, against a small pis- 
ton in the cylinder of the indicator, which 
in turn is controlled or resisted in its 
movement by a spring of known tension, 
so as to confine the stroke of the indica- 
tor piston within a certain small limit. 
Second, the stroke of the indicator pis- 
ton is communicated by a multiplying 
mechanism of levers and parallel motion 
to a pencil moving in a vertical straight 
line, the distance through which the pencil moves being 
governed by the pressure in the engine-cylinder and the 
tension of the spring. Third, by the intervention of a re- 
ducing mechanism and a strong cord, the motion of the pis- 
ton of the engine throughout an entire revolution is com- 
municated to a small drum attached to and forming a part 
of the indicator. The movement of the drum is rotative 
and in a direction at right angles to the movement of the 
pencil. The forward stroke of the engfine-piston causes 




Fig. 173. 

Crosby Indicator 

Spring. 



273 



QUESTIONS AND ANSWERS 



the drum to rotate through part of a revolution and at 
the same time a clock-spring connected within the drum 
is wound up. On the return stroke the motion of the 
drum is reversed, and the tension of the spring returns 
the drum to its original position and also keeps the cord 
taut 

Ques. 630. — Describe in general terms the construc- 
tion of an indicator. 

Ans. — An indicator con- 
sists of a small cylinder, 
open to the atmosphere at 
the top and having its bot- 
tom end connected by suit- 
able pipes and stop-cocks 
to both ends of the engine- 
cylinder in such a manner 
that the steam-pressure in 
either end may be caused 
to act upon the indicator 
piston, as required. The 
cylinder of the indicator 
stands vertical, and is of a known area, usually about one 
square inch. It contains a piston, upon which the steam 
acts only on the under side, the top of the cylinder being 
open to the atmosphere. The length of stroke of this 
piston is regulated and controlled by a steel spiral spring 
of known tension, which acts in resistance to the pressure 
of the steam. When the cock connecting the cylinders of 
the engine and indicator is closed, both ends of the indi- 
cator cylinder are open to atmospheric pressure, and the 




Fig. 174. 
Sectional View Thompson Indicator. 



THE INDICATOR — PRINCIPLES OF INDICATOR 



273 



pencil, which is connected to the piston by a system of 
levers, stands at its neutral position. 

Ques. 631. — Describe the construction and action f/^ 
the spiral spring in connection with the indicator pistai. 

Ans. — These springs are made of different tensioj.s in 
order to be suitable to different steam-pressure? and 
speeds, and are numbered 20, 40, 60, etc., the number 
meaning that a pressure per square inch 
in the engine-cylinder corresponding to 
the number on the spring will cause a 
vertical movement of the pencil through 
a distance of one inch. Thus, if a No. 
20 spring is used and the pressure in the 
cylinder at the commencement of the 
stroke is 20 pounds per square inch, the 
pencil will be raised one inch, or if the 
pressure is 30 pounds, the pencil will 
travel l]^ inch, and if there is a vacuum 
of 20 inches in the condenser, the pencil 
will drop /^ inch below the atmospheric 
line for the reason that 20 inches of vac- 
uum correspond to a pressure of about 
10 pounds less than atmospheric pressure or an absolute 
pressure of about 4 pounds. If a 60 spring is used a 
pressure of 60 pounds in the engine-cylinder will be re- 
quired to raise the pencil one inch, or 90 pounds to raise 
it 1/^ inch. 

Ques. 632. — Are these springs placed inside the 
cylinder in all types of indicators? 

Ans. — The Ashcroft Manufacturing Company of New 




Fig. 175. 
Thompson Indica- 
tor Spring. 



274 



QUESTIONS AND ANSWERS 



York, makers of the well-known Tabor indicator, have 
recently introduced a new feature in indicator work by 
connecting the spring on top of the cylinder and in plain 




Fig. 176. Improved Tabor Indicator with Outside Connected Spring. 

AsHCROFT Mfg. Co., N. Y. 



view of the operator. This arrangement removes the 
spring from the influence of direct contact with the 
steam, and it is subject only to the temperature of the 



THE INDICATOR PRINCIPLES OF INDICATOR 275 

surrounding atmosphere. It is claimed that as a result 
of this the accuracy of the spring is insured and that no 
allowance need to be made in its manufacture for 
expansion caused by the high temperature to which it is 
'subject when located within the cylinder. Another good 
feature of this design is, that the spring can be easily 
removed without disconnecting any one part of the 
instrument in case it is desired to change springs. 

Ques. 633. — What precautions should be observed in 
attaching the indicator to an engine-cylinder? 

Ans. — The main requirements in these connections 
are that the holes shall not be drilled near the bottom of 
the cylinder where water is likely to find its way into 
the pipes, neither should they be in a location where the 
inrush of steam from the ports will strike them directly^ 
nor where the edge of the piston is liable to partly cover 
them when at its extreme travel. An engineer before he 
undertakes to indicate an engine shoull satisfy himself 
that all these requirements are fulfilled. Otherwise he is 
not likely to obtain a true diagram. The cock supplied 
with the indicator is threaded for one-half inch pipe, and 
unless the engine has a very long stroke i^ is the practice 
to bring the 'two end connections together at the side or 
top of the cylinder and at or near the middle of its length, 
where they can be connected to a three-way cock. The 
pipe connections should be as short and as free from 
elbows as possible, in order that the steam may strike 
the indicator piston as nearly as possible at the same 
moment that it acts upon the engine-piston. These pipes, 
should always be thoroughly blown out and cleaned, by 



276 QUESTIONS AND ANSWERS 

allowing the steam to blow through the open three-way 
cock during several revolutions of the engine before con- 
necting the indicator. If this is not done there is a moral 
certainty that dirt and grit will get into the cylinder of 
the indicator and cause it to work badly and give 
diagrams that are misleading. 

Ques. 634. — How is an indicator diagram or card 
drawn? 




Fig. 177. Three-way Cock. 



Ans. — To the outside of the drum a piece of blank 
paper of suitable size is attached and held in place by two 
clips. Upon this paper the pencil in its motion up and 
down traces a complete diagram of the pressures and 
other interesting events transpiring within the engine- 
cylinder during the revolution of the engine. In fact, the i 
diagram traced upon the paper is the compound result of \ 
two concurrent movements. First, that of the pencil ♦ 
caused by the pressure of the steam against the indicator j 



THE INDICATOR PRINCIPLES OF INDICATOR 277 

piston; second, that of the paper drum caused by, and 
coincident with the motion of the engine-piston. 

Ques. 635. — How is the atmospheric line drawn? 

Ans. — By holding the pencil to the paper, and causing 
the drum to be rotated, when the pencil stands at its neutral 
position, that is with the steam shut off from the indica- 
tor cylinder. 

Ques. 636. — What is meant by the term atmospheric 
line? 

Ans. — The atmospheric line is a horizontal line drawn 
on the diagram and means the line of atmospheric pres- 
sure. If the engine is a non-condensing engine the pencil 
in tracing the diagram will, or at least should not fall 
below the atmospheric line at any point, but will on the 
return stroke trace a line called the line of back pressure 
at a distance more or less above the atmospheric line and 
very nearly parallel with it. If the engine is a condensing 
engine the pencil will drop below the atmospheric line 
while tracing the line of back pressure on the diagram, 
and the distance this line is below the atmospheric line 
will depend upon the number of inches of vacuum in the 
condenser. 

Ques. 637. — Is the atmospheric line a necessary part 
of an indicator diagram? 

Ans. — The atmospheric line is a very important factor 
in the study of the diagram. 

Ques. 638. — How are the dimensions of the diagram 
regulated? 

Ans. — It is a convenient practice to select a spring 
numbered one-half of the boiler-pressure as, for instance, 



278 



QUESTIONS AND ANSWERS 



suppose gauge-pressure or boiler-pressure is 200 pounds 
per square inch, then a 100 spring would give a diagram 
2 inches in height, which is a convenient height. As to 
the length of the diagram, this is regulated by adjustment 




Fig. 178. Crosby Reducing Wheei, Attached to Indicator. 



of the cord in its travel, by means of the reducing wheel 
Any length of diagram up to four inches may be obtained, 
but two and a half to three inches is a very good length 
for analysis. 

Ques. 639. — How is the motion of the crosshead of 



THE INDICATOR PRINCIPLES OF INDICATOR 



279 



the engine reduced and utilized for rotating the drum of 
the indicator? 

Ans. — There are various mechanisms used for this 
purpose. Probably the only practically universal 




mechanism tor reducing the motion of the crosshead is 
the reducing wheel, a device in which, by the employment 
of gears and pulleys of different diameters, the motion is 
reduced to within the compass of the drum, and the 



280 



QUESTIONS AND ANSWERS 



device is applicable to almost any make of engine, 
whether of high or low speed.. Some makers of indicators 
attach the reducing wheel directly to the indicator, thus 
producing a neat and very convenient arrangement. 

Ques. 640. — Describe the construction of the wooden 
pendulum for reducing the motion. 

Ans. — It consists of a flat strip of pine or other light 





Wooden Pendulum, Reducing Motion. 

wood of a length not less than one and a half times the 
stroke of the engine, and if made longer it will be better. 
It should be from 54 to ?^ mch thick and have an average 
width of about 4 inches. If the engine to be indicated is 
horizontal the bar or pendulum is to be pivoted at a fixed 
point directly above and in line with the side of the cross- 
head, as that is generally the mo^t convenient point of 
attachment. The pivot can be fixed to a permanent 



THE INDICATOR — PRINCIPLES OF INDICATOR 281 

Standard bolted to the frame of the engine or it may be 
secured to the ceiling of the room or even to a post 
fastened to the floor. If the engine is vertical the bar 
can be pivoted to the wall of the room or a strong post 
firmly secured to the floor. The connection with the 
crosshead is best accomplished by means of a short bar or 
link. A convenient length for this bar is one-half the 
stroke of the engine. 

Ques. 641. — When the short bar is one-half the 
length of the stroke, how is the correct point for the loca- 
tion of the pivot for the pendulum found? 

Ans. — Place the engme on the center with the cross- 
head at the end of the stroke towards the crank. Then 
having previously bored a hole for the pivot in one end 
of the pendulum bar and in the other end a hole for con- 
necting with the link, <^risoend the pendulum by a 
temporary pin, as a large wood screw, directly above and 
in line with the stud or bolt hole which has previously 
been tapped into the crosshead at any convenient point. 
The pendulum should be temporarily suspended at such 
a height that when it hangs perpendicular the hole in its 
lower end will line up accurately with the hole or stud in 
the crosshead. Now swing the pendulum in either direc- 
tion a distance equal to the length of the link (one-half 
the stroke of the engine) from the crosshead connection 
and note the distance that the bottom hole is above a 
straight edge laid horizontal and in line with the center 
of the stud in the crosshead. This will give the total 
vibration of the free end of the link from a line parallel 
with the line of the engine and the permanent location of 



382 QUESTIONS AND ANSWERS 

the pivot should be one-half of this distance below the 
temporary point of suspension. This will allow the link 
to vibrate equally above and below the center of its con- 
nection with the crosshead. 

Ques. 642. — How is the correct point of attachment 
of the cord to the pendulum found? 

Ans. — The cord can be attached to the pendulum at a 
point near the pivot, which will give the desired length of 
diagram. This point can be determined by multiplying 
the length of the pendulum by the desired length of dia- 
gram and dividing the product by the stroke. For 
convenience these terms should be expressed in inches. 
Thus, assume stroke of engine to be 48 inches, length of 
pendulum VA times length of stroke = 72 inches. 
Desired length of diagram 3 inches. Then 72X3-^48 = 4.5 
inches, which is the distance from center of pivot to point 
of connection for the cord. This can be either a small 
hole bored through the pendulum or a wood screw to 
which the cord can be attached. From this point the 
cord should be led over a guide pulley located at such 
height that when the pendulum is vertical the cord will 
leave it at right angles. After leaving the guide pulley 
the cord can be carried at any angle desired. 

Ques. 643. — How shoulu the indicator be cared for? 

Ans. — ^The indicator should be cleaned and oiled 
both before and after using. The best material for 
wiping it is a clean piece of old soft muslin of fine texture, 
as there is not so much liability of lint sticking to or 
getting into the small joints. Use good clock oil for the 
joints and springs, and before taking diagrams it is a good 



( 



THE INDICATOR PRINCIPLES OF INDICATOR 283 

practice to rub a small portion of cylinder oil on the 
piston and the inside of the cylinder, but when about to 
put the instrument away these should be oiled with clock 
oil also. 

Ques. 644. — How may the cord be adjusted to proper 
llength? 

Ans. — None but the best cord should be used for con- 
necting the paper drum with the reducing motion, as a 
cord that is liable to stretch will cause trouble. After 
the indicator has been screwed on to the cock connecting 
with the pipe, the cord must be adjusted to the proper 
length before hooking it on to the drum. This must be 
done while the engine is running, by taking hold of the 
loop on the cord connected with the reducing motion 
with one hand, and with the other hand grasp the hook 
on the short cord attached to the drum, then by holding 
the two ends near each other during a revolution or two 
it will be seen whether the long cord needs to be shortened 
or lengthened. 

Ques. 645. — What precautions are necessary in regard 
to the paper and pencil in order to secure a truthful 
diagram? 

i Ans. — Care should be exercised in placing the paper 
on the drum to see that it is stretched tight and firmly 
held by the clips. The pencil point having been first 
sharpened by rubbing it on a piece of fine emery cloth or 
sand paper should be adjusted by means of the pencil 
stop with which all indicators should be provided, so that 
it will have just sufficient bearing against the paper to 
make a fine, plain mark. If the pencil bears too hard on 



284 QUESTIONS AND ANSWERS 

the paper it will cause unnecessary friction and the dia- 
gram will be distorted. The best method of ascertaining 
this fact and also whether the travel of the drum is 
equally divided between the stops, is to place a blank dia- 
gram on the drum, connect the cord and while the engine 
makes a revolution hold the pencil against the paper. 
Then unhook the cord, remove the paper and if the travel 
of the drum is not divided correctly it can be changed. 

Ques. 646. — Describe the process of taking an indica- 
tor diagram. 

Ans. — Place a fresh blank on the drum, being careful 
to keep the pencil out of contact with it, connect the cord, 
open the cock admitting steam to the indicator and after 
the pencil has made a few strokes to allow the cylinder to 
become warmed up, then gently swing it around to the 
paper drum and hold in there while the engine makes a 
complete revolution. Then move the pencil clear of the 
paper, close the cock and unhook the cord. Now trace 
the atmospheric line by holding the pencil against the 
paper while the drum is revolved by hand. This method 
of tracing the atmospheric line is preferable to that of 
tracing it immediately after closing the cock and while 
the drum is still being moved by the engine, for the reason 
that there is not so much liability of getting the atmos- 
pheric line too high owing to the presence of a slight 
pressure of steam remaining under the indicator piston 
for a second or two just after closing the cock; also the 
line drawn by hand will be longer than one drawn while 
the drum is moved by the motion of the engine and will 
therefore be more readily distinguished from the line of 
back pressure. 



THE INDICATOR — PRINCIPLES OF INDICATOR 38^ 

Ques. 647. — What other details should (jc ofesenrcd in 
the taking of indicator diagrams? 

Ans. — As soon as the diagrams are taken the foISovving 
data should be noted upon them: The end of the cyh'nder, 
whether head or crank; boiler-pressure, and time when 
taken. Other data can be added afterwards. 

Ques. 648. — What needed changes in the cut-off of a 
Corliss engine, as shown by a diagram, may be made while 
the engine is running? 

Ans. — If the engine is an automatic cut-off of the 
Corliss type and the point of cut-off on one end does not 
coincide with the other, the difference can generally be 
adjusted while the engine is running by changing the 
length of the rods extendmg from the governor to the 
tripping device. These rods are^ or shoula be fitted with 
right and left threads on the ends for this purpose. Any 
changes in the valves, such as giving them more lead, 
compression, etc., and which necessitates changing the 
length of the reach rods connecting them with the wrist 
plate, will have to be made while the engine is stopped, 
although with slow-speed engines and the exercise of 
caution it is possible to make alterations in these rods 
while the engine is running. 

Ques. 649. — What important details will a truthful 
indicator diagram show? 

Ans. — First, the pressure of the steam against the 
piston of the engine at any point in the stroke during a 
complete revolution; second, diagrams from a condensing 
engine show the amount of vacuum that is being main- 
tained in the condenser, measured from the line of perfect 



286 QUESTIONS AND ANSWERS 

vacuum; third, the point of cut-off is clearly shown, also 
the point in the return stroke at which compression 
begins; fourth, the expansion curve, and how near it 
approaches the theoretical expansion curve; fifth, any 
fault in the setting of the valves is clearly shown on 
the diagram; sixth, diagrams taken from the different 
cylinders of a compound or stage expansion engine may 
be combined in such a manner as to show whether or not 
the cylinders are properly proportioned, and whether the 
steam is being distributed correctly. 

Ques. 650. — What is absolute pressure? 

Ans. — Pressure reckoned from a perfect vacuum. It 
equals the boiler-pressure plus the atmospheric pres- 
sure. 

Ques. 651 — What is boiler-pressure or gauge-pres- 
sure? 

Ans. — Pressure above the atmospheric pressure as 
shown by the steam gauge. 

Ques. 652. — What is initial pressure? 

Ans. — Pressure in the cylinder at the beginning of the 
stroke. 

Ques. 653. — What is meant by terminal pressure (T, 

p.)? 

Ans. — The pressure that would exist in the cylinder 
at the end of the stroke provided the exhaust valve did 
not open until the stroke was entirely completed. It 
may be graphically illustrated on the diagram by extend- 
ing the expansion curve by hand to the end of the stroke. 
It is found theoretically by dividing the pressure at point 
of cut-oflF by the ratio of expansion. Thus, absolute 



THE INDICATOR — PRINCIPLES OF INDICATOR 287 

pressure at cut-off=100 pounds, ratio of expansion = 5; 
then 100-^5 = 20 pounds, absolute terminal pressure. 

Ques. 654.~What is mean effective pressure (M. E. 
P.)? 

Ans. — The average pressure acting upon the piston 
throughout the stroke minus the back pressure. 

Ques. 655. — What is back pressure? 

Ans. — Pressure which tends to retard the forward 
stroke of the piston. Indicated on the diagram from a 
non-condensing engine by the height of the back pressure 
line above the atmospheric line. In a condensing engine 
the degree of back pressure is shown by the height of the 
back pressure line above an imaginary line representing the 
pressure in the condenser corresponding to the degree 
of vacuum in inches, as shown by the vacuum gauge. 

Ques. 656.— What is total or absolute back pressure? 

Ans. — Total or absolute back pressure, in either a 
condensing or non-condensing engine, is that indicated 
on the diagram by the height of the line of back pressure 
above the line of perfect vacuum. 

Ques. 657. — How is the line of perfect vacuum drawn 
on an indicator diagram? 

Ans. — The line of perfect vacuum is drawn parallel 
with the atmospheric line and at a distance below the 
latter, representing 14.7 pounds, as measured by the scale 
corresponding to the spring that was used in taking the 
diagram. Different scales are supplied for the different 
springs used. 

Ques. 658. — What is meant by ratio of expansion? 

Ans. — The oroDortion that the volume of steam in the 



288 QUESTIONS AND ANSWERS 

cylinder at point of release bears to the volume at cut-off. 
Thus, if the point of cut-off is at one-fifth of the stroke, 
and release does not take place until the end of the stroke, 
the ratio of expansion, or in other words, the number of 
expansions, is 5. When the T. P. is known the ratio of 
expansion ma}^ be found by dividing the initial pressure 
by the T. P. 

Ques. 659. — ^"^Vhat is: neart by wire drawing? 

Ans. — When through insufficiency of valve opening, 
contracted ports or throttling governor, the steam is 
prevented from following up the piston at full initial 
pressure until the point of cut-off is reached, it is said to 
be wire drawn. It is indicated on the diagram by a 
gradual inclination downwards of the steam line from 
the admission line to the point of cut-off. Too small a 
steam pipe from boiler to engine will also cause wire 
drawing and fall of pressure. 

Ques. 660. — What is condenser pressure? 

Ans. — Condenser pressure may be defined as the pres- 
sure existing in the condenser of an engine, caused by 
the lack of a perfect vacuum. As, for instance, with a 
vacuum of 25 inches there will still remain the pressure 
due to the 5 inches which is lacking. This will be about 
2.5 pounds. 

Ques. 661. — What is absolute zero? 

Ans. — Absolute zero has been fixed by calcula- 
tion at 461.2 degrees below the zero of the Fahrenheit 
scale. 

Ques. 662.— What is piston displacement? 

Ans. — The space or volume swept through by the 



THE INDICATOR — PRINCIPLES OF INDICATOR 289 

piston in a single stroke. Found by multiplying the 
area of piston by length of stroke. 

Ques. 663. — What is piston clearance? 

Ans. — The distance between the piston and cylinder 
head when the piston is at the end of the stroke. 

Ques. 664. — What is steam clearance, ordinarily 
termed clearance? 

Ans. — The space between the piston at the end of the 
stroke and the valve face. It is reckoned in per cent 
of the total piston displacement. 

Ques. 665. — What is the meaning of the expression 
horse-power as applied to a steam-engine? 

Ans. — 33,000 pounds raised one foot high in one 
minute of time. 

Ques. 666. — -What is indicated horse-power (I. H. P.)? 

Ans. — The horse-power as shown by the indicator 
diagram. It is found as follows: Area of piston in 
square inchesXM. E. P. X^iston speed in feet-^33,000. 

Ques. 667. — What is meant by the term piston speed? 

Ans. — The distance in feet traveled by the piston in 
one minute. It is the product of twice the length of 
stroke expressed in feet multiplied by the number of 
revolutions per minute. 

Ques. 668. — What is net horse-power? 

Ans. — I. H. P. minus the friction of the engine 

Ques. 669. — What is compression? 

Ans. — The action of the piston as it nears the end of 
the stroke, in reducing the volume and raising the pres- 
sure of the steam retained in the cylinder ahead of the 
piston by the closing of the exhaust valve. 



290 QUESTIONS AND ANSWERS 

Ques. 670. — What is Boyle's law of expanding gases? 

Ans.— *'The pressure of a gas at a constant tempera- 
ture varies inversely as the space it occupies." Thus, 
if a given volume of gas is confined at a pressure of 
50 pounds per square inch and it is allowed to expand to 
twice its volume, the pressure will fall to 25 pounds per 
square inch. 

Ques. 671. — What is an adiabatic curve? 

Ans. — A curve representing the expansion of a gas 
which loses no heat while expanding. Sometimes called 
the curve of no transmission. 

Ques. 672. — What is an isothermal curve? 

Ans. — A curve representing the expansion of a gas 
having a constant temperature but partially influenced 
by moisture, causing a variation in pressure according 
to the degree of moisture or saturation. It is also called 
the theoretical expansion curve. 

Ques. 673. — What is the expansion curve? 

Ans. — The curve traced upon the diagram by the 
indicator pencil showing the actual expansion of the steam 
in the cylinder. 

Ques. 674. — What is power? 

Ans. — The rate of doing work, or the number of foot 
pounds exerted in a given time. 

Ques. 675. — What is the unit of work? 

Ans. — The foot pound, or the raising of one pound 
weight one foot high. 

Ques. 676. — Define the first law of motion. 

Ans. — All bodies continue either in a state of rest of 
of uniform motion in a straight line, except in so far as 



THE INDICATOR PRINCIPLES OF INDICATOR 291 

they may be compelled by impressed forces to change that 
state. 

Ques. 677.— What is work? 

Ans. — Mechanical force or pressure can not be con- 
sidered as work unless it is exerted upon a body and 
causes that body to move through space. The product 
of the pressure multiplied by the distance passed through 
and the time thus occupied is work. 

Ques. 678. — What is momentum? 

Ans. — Force possessed by bodies in motion, or the 
product of mass and density. 

Ques. 679. — What is the meaning of the word dynam- 
ics? 

Ans. — The science of moving powers or of matter in 
motion, or of the motion of bodies that mutually act upon 
each other. 

Ques. 680.— What is force? 

Ans. — That which alters the motion of a body or puts 
in motion a body that was at rest. 

Ques. 681. — What is the maximum theoretical dut}? 
of steam? 

Ans.— The maximum theoretical duty of steam is the 
product of the mechanical equivalent of heat, viz., 778 
foot pounds multiplied by the total heat units in a 
pound of steam. Thus, in one pound of steam at 212 
degrees reckoned from 32 degrees the total heat equals 
1,146.6 heat units. Then 778X1.146.6 = 892,054.8 foot 
oounds= maximum duty. 

Ques. 682. — What is steam efficiency? 

Ans. — Steam efficiency mav be expressed as follows; 



292 QUESTIONS AND ANSWERS 

Heat converted into useful work . 

TT Z ~T~j and maximum efficiency 

can only be attained by using steam at as high an initial 
pressure as is consistent with safety, and at as large a 
ratio of expansion as possible. 

Ques. 683. — What is meant by the term efficiency of 
the plant as a whole? 

Ans. — Efficiency of the plant as a whole includes 
boiler and engine efficiency, and is to be figured upon the 
, . - Heat converted into useful work 
Calorific or heat value of fuel 

Ques. 684. — What is the horse-power constant of an 
engine? 

Ans. — The horse-power constant of an engine is found 
by multiplying the area of the piston in square inches by 
the speed of the piston in feet per minute and dividing 
the product by 33,000. It is the power the engine would 
develop with one pound mean effective pressure. To find 
the horse-power of the engine, multiply the M. E. P. of 
the diagram by this constant. 

Ques. 685. — What is meant by the expression steam 
consumption per horse-power per hour? 

Ans. — The weight in pounds of steam exhausted into 
the atmosphere or into the condenser in one hour divided 
by the horse-power developed. It is determined from the 
diagram by selecting a point in the expansion curve just 
previous to the opening of the exhaust-valve and 
measuring the absolute pressure at that point. Then the 
piston displacement up to the point selected, plus 
the clearance space, expressed in cubic feet, will' 



THE INDICATOR PRINCIPLES OF INDICATOR 293 

give the volume of steam in the cylinder, which multiplied 
by the weight per cubic foot of steam at the pressure 
as measured will give the weight of steam consumed during 
one stroke. From this should be deducted the steam 
saved by compression as shown b}^ the diagram, in order 
to get a true measure of the economy of the engine. 
Having thus determined the weight of steam consumed 
for one stroke, multiply it by twice the number of 
strokes per minute and by 60, which will give the total 
weight consumed per hour. This divided by the horse- 
power will give the rate per horse-power per hour. 

Ques. 686. — What is cylinder condensation and 
reevaporation? 

Ans. — When the exhaust-valve opens to permit the 
exit of the steam there is a perceptible cooling of the 
walls of the cylinder, especially in condensing engines 
when a high vacuum is maintained. This results in 
more or less condensation of the live steam admitted by 
the opening of the steam-valve; but if the exhaust- 
valve is caused to close at the proper time so 
as to retain a portion of the steam to be compressed by 
the piston on the return stroke, a considerable poition 
of the water caused by condensation will be reevaporated 
into steam by the heat and consequent rise in pressure 
caused by compression. 

Ques. 687. — What are ordinates, as applied to indi- 
cator diagrams? 

Ans. — Parallel lines drawn at equal distances apart 
across the face of the diagram and perpendicular to the 
atmospheric line. They serve as a g:uide to facilitate the 



294 



QUESTIONS AND ANSWERS 



measurement of the average forward pressure through- 
out the stroke, or the pressure at any point of the stroke 
if desired. 

Ques. 688. — What is a throttling governor? 

Ans. — A governor that is used to regulate the speed 
of engines having a fixed cut-off. The governor controls 
the position of a valve in the steam-pipe, opening or clos^ 



V 


•9 




5 ^ ^ r 


* 
i 


■y 
















K| 


/ 










^5 


i 








y 








- 


\ 




^^' 










i^ 


i: 




-^5^ 
^ 








t 





Fig. 180. Illustrating the Process of Obtaining the Mean KFf'ECTivfi 
Pressure by Means of Ordinates. 

ing it according as the engine needs more or less steam in 
order to maintain a regular speed. 

Ques. 689. — What is an automatic or variable cut- 
off engine? 

AnSo — In engines of this type the full boiler pressure 
is constantly in the valve chest and the speed of the 
engine is regulated by the governor controlling the point 
of cut-off, causing it to take place earlier or later 
according as the load on the engine is lighter or heavier. 



THE INDICATOR PRINCIPLES OF INDICATOR 295 

Ques. 690.— What is a fixed cut-off? 

Ans. — This term is applied to engines in which the 
point of cut-off remains the same regardless of the load, 
the speed being regulated by a throttling governor. 

Ques. 691. — What is an adjustable cut-off? 

Ans. — One in which the point of cut-off may be regu- 
lated or adjusted by hand by means of a hand wheel and 
screw attached to the valve stem, the supply of steam 
being regulated by a throttling governor. 

Ques. 692. — What is an isochronal or shaft governor? 




Fig. 181. Indicator Diagram Taken from a Condensing Engine. 

A, atmospheric line. V, line of perfect vacuum. B to D, admission line. 
D to E), steam line. E, point of cut-off. E to F, expansion line. F to G, ex- 
haust. G>to C, line of back pressure; and from C to B shows compression. 



r~ Ans. — This device in which the centrifugal and cen- 
tripetal forces are utilized, as in the fly-ball governor, is 
generally applied to automatic cut-off engines having 
reciprocating or slide valves. It is attached to the crank 
shaft and its function is to change the position of the 
eccentric, which is free to move across the shaft within 
certain prescribed limits, but is at the same time attached 
to the governor. The angular advance of the eccentric 
is thus increased or diminished: in fact is entirely under 



296 



QUESTIONS AND ANSWERS 



the control of the governor, and cut-off occurs earlier or 
later according to the demands of the load on the 
engine. 

Ques. 693. — If the valves of an engine are properly 
adjusted and the distribution of the steam is approxi- 
mately correct, what particular features should character- 
ize an indicator diagram taken from it? 

Ans. — First, the admission line at the beginning of the 
stroke should be perpendicular to the atmospheric line; 
second, the steam line, as it is called, extending from the 
beginning of the stroke to the point of cut-off, should be 




Fig. 182. Diagram Showing Insufficient Lead. 



parallel with the atmospheric line; third, the point of 
cut-off should be sharply defined; fourth, the expansion 
curve, extending from the point of cut-off to the point of 
release, should conform as near as possible with the 
isothermal curve, which can easily be applied to any dia- 
gram; fifth, the exhaust line, extending from point of 
release to that point in the return stroke where compres- 
sion begins, should be parallel with and practically coin- 
cident with the atmospheric line, if the engine is 
non-condensing, or if the engfine be a condensing engine. 



THE INDICATOR PRINCIPLES OF INDICATOR 297 

this line should approach within a few pounds of the line 
of perfect vacuum. ' 

Ques. 694. — If the admission line inclines inward 
from the perpendicular, what defect in the valve setting 
is indicated? 

Ans. — Insufficient lead. 

Ques. 695.— How is wire drawing of the steam 
detected by the indicator diagram? 

Ans. — By the downward inclination of the steam line 
toward the point of cut-ofif. 




Fig. 183. Diagram Showing Ei-i-ects of Wire; Drawing the Steam. 

Ques. 696. — What is a very necessary factor in the 
calculation of the horse-power of an engine as shown by 
a diagram taken from it? 

Ans. — ^The mean effective pressure. 

Ques. 697. — How is the M. E. P. of a diagram ascer- 
tained? 

Ans. — There are two methods commonly used. First, 
by means of ordinates, and secondly, by the use of the 
planimeter. 



898 



QUESTIONS AND ANSWERS 



Ques. 698. — Describe the method of finding the M. 
E.. P. by ordinates. 

Ans. — The process consists in drawing any convenient 
number of vertical lines perpendicular to the atmospheric 
line across the face of the diagram, spacing them equally, 
with the exception of the two end spaces, which should 
be one-half the width of the others, for the reason that 
the ordinates stand for the centers of equal spaces. This 
is an important matter, and should be thoroughly under- 



4^ 

ss 

fo.f 
8 
7 





Er^.i 
















C-zf/rA 


.■ni 








h ^ 








i 


t 


z 


^ 


\. 


X 

■J- 




"^ 


"3" 


^i 


h 






B' 



^? 

/<^ 
J S.I 

J I, I 

7'^ 






M^^^r. 



^ J2 .3r/c . ijui[^£p 



Fig. 184. Finding M. E. P. 



stood, because if the spaces are all made of equal width, 
and measurements are taken on the ordinates, the results 
will be incorrect, especially in the case of high initial pres- 
sure and early cut-ofif, following which the steam undergoes 
great changes. If the spaces are all made equal, the meas- 
urements will require to be taken in the middle of them, and 
errors are liable to occur, whereas if spaced as before 
described, the measurements can be made on the ordinates, 
which is much more convenient and will insure correct 
results. Any number of ordinates can be drawn, but ten 



THE INDICATOR PRINCIPLES OF INDICATOR 



299 



is the most convenient and is amply sufficient, except in 
case the diagram is excessively long. 

Ques. 699. — Having succeeded in drawing the ordi- 
nates across the face of the diagram, what is the next step? 

Ans. — The pressure represented by each line is meas- 
ured from the exhaust line to the steam line, and so on. 




Fig. 185. Planimeter. 

along the expansion curve throughout the length of the 
diagram, using for this purpose the scale adapted to the 
fpring used, and having thus obtained measurements on 
each line, add all together and divide the sum total by 
the number of lines, which will give the mean forward 
pressure. To obtain the mean effective pressure, deduct 
the back pressure, which is represented by the distance 



300 



QUESTIONS AND ANSWERS 



of the exhaust line above the atmospheric line in a non- 
condensing engine, and in a condensing engine the back 
pressure is measured from the line of perfect vacuum. 




Fig. 186. Coffin Averager or Pi^animeter. 



Ques. 700. — What is a planimeter? 

Ans. — The planimeter is an instrument which will 



THE INDICATOR PRINCIPLES OF INDICATOR 301 

accurately measure the area of any plane surface, no 
matter how irregular the outline or boundary line is. 

Ques. 701. — What is the main requirement in ascer- 
taining the M. E. P. of a diagram? 

Ans. — The prime requisite In making power calcula- 
tions from indicator diagrams is to obtain the average 
height or width of the diagram, supposing it were reduced 
to a plain parallelogram instead of the irregular figure 
which it is. 

Ques. 702. — What advantage is gained by using the 
planimeter in measuring diagrams? 

Ans. — It shows at once the area of the diagram in 
square inches and decimal fractions of a square inch, and 
when the area is thus known it is an easy matter to obtain 
the average height by simply dividing the area in inches 
by the length of the diagram in inches. Having ascer- 
tained the average height of the diagram in inches or 
fractions of an inch the mean or average pressure is 
found by multiplying the height by the scale. Or the 
process may be made still more simple by first multiplying 
the area, as shown by the planimeter in square inches and 
decimals of an inch, by the scale and dividing the product 
by the length of the diagram in inches. The result will 
be tlie same as before, and troublesome fractions will be 
avoided. 

Ques. 703.— Having obtained the M. E. P., as shown 
by the diagram, how may the horse-power developed by 
the engine be ascertained? 

Ans. — The area of the piston (minus one-half the are^ 
of rod) multiplied by the M. E. P., as shown by the dia- 



303 QUESTIONS AND ANSWERS 

gram, and this product multiplied by the number of feet 
traveled by the piston per minute (piston speed) will give 
the number of foot pounds of work done by the engine 
each minute, and if this product be divided by 33,000, 
the quotient will be the indicated horse-power (I. H. P.) 
developed by the engine. 

Ques. 704. — Mention two important factors in calcu- 
lations of steam consumption. 

Ans. — In calculating the steam consumption of an 
engine, two very important factors must not be lost sight 
of, viz., clearance and compression. Especially is this 
the case in regard to clearance when there is little or no 
compression, for the reason that the steam required to fill 
the clearance space at each stroke of the engine is prac- 
tically wasted, and all of it passes into the atmosphere or 
the condenser, as the case may be, without having done 
any useful work except to merely fill the space devoted to 
clearance. On the other hand, if the exhaust valve is 
closed before the piston completes the return stroke, the 
steam then remaining in the cylinder will be compressed 
into the clearance space and can be deducted from the 
total volume which, without compression, would have been 
exhausted at the terminal pressure. 

Ques. 705. — When, owing to light load and early 
cut-off, the expansion curve drops below the line of back 
pressure, how must the area of the diagram be calculated? 

Ans. — The area of the loop below the back pressure 
line must be subtracted from the remainder of the diagram. 
If the planimeteris used, the instrument will make the sub- 
traction automatically, but if the diagram is divided into 



THE INDICATOR PRINCIPLES OF INDICATOR 



303 



parts by ordinates, the pressure shown by the ordinates in 
the lower loop must be subtracted from that shown by 
the loop above the back pressure line in order to ascertain 
the M. E. P. or average pressure. 

Ques. 706. — What is meant by the adiabatic curve? 



T 




ic 


s 

■ ^0 






■ 7^ 




/ X 


. 7o 




/ / 


Tf 




/ / 


■ 6o 




/ y 


5S 




yy 


. 5q 




.^^ 


HS 




.-^ 






..^^ 


35 




.^.^^ 


. 3o 


R 




zL 


c 


•^ J 


A 


V 


y 



Fig. 187. 

The dotted line R C shows what the true adiabatic curve would be on the 
diagram, provided it could be realized. 



Ans. — If it were possible to so protect or insulate the 
cylinder of a steam engine that there would be absolutely 
no transmission of heat either to or from the steam dur- 
ing expansion, a true adiabatic curve or **curve of no 
transmission*' might be obtained. The closer the actual 
expansion curve of a diagram conforms to such a curve, 
the higher will be the efficiency of the engine as a 
machine for converting heat into work. 



CHAPTER X 

THE STEAM TURBINE FUNDAMENTAL PRINCIPLES 

Ques. 707. — What are the basic principles governing 
the action of steam turbines? 

Ans. — There are wo fundamental principles upon 
which all steam turbines operate, viz., reaction and 
impulse. In some types of turbines the reaction principle 
alone is utilized, and in others the impulse, while in still 
others, and probably the most successful ones, both 
principles are combined. 

Ques. 708. — In what general direction does the steam 
flow w^hen used in a turbine? 

Ans. — Parallel with the shaft or rotor, and also in a 
screw-like direction around it. This definition does not 
apply, however, to turbines of the purely impulse type, 
like the De Laval, for instance. 

Ques. 709. — What causes the rotor to revolve? 

Ans. — The action of the steam, coming, as it does, 
with tremendous velocity and great force against the 
small buckets or vanes w4th w^hich the rotor is fitted, 
causes it to revolve, and as there is a continuous current 
of steam passing into the cylinder, the motion is continu- 
ous. 

Ques. 710. — W^hat law of turbo-mechanics governs 
the relation of bucket-speed, and fluid or steam speed? 

Ans. — For purely impulse-wheels, bucket-speed equals 
one-half of jet-speed. For reaction wheels, bucket-speed 
equals jet-speed. 

.304 



STEAM TURBINE FUNDAMENTAL PRINCIPLES 305 

Ques. 711. — With what velocity would steam of 100 
pounds pressure discharge into a vacuum of 28 inches? 

Ans. — The theoretical velocity would be 3,860 feet per 
second. 

Ques. 712. — What amount of energy would a cubic 
foot of steam under 100 pounds pressure exert if allowed 
to discharge into a vacuum of 28 inches? 

Ans. — 59,900 foot pounds. 

Ques. 713.— Does the steam impinge against the first 
rows or sections of buckets at full pressure? 

Ans. — In turbines of the Parsons type, the initial 
pressure of the steam is practically boiler-pressure, but 
it gradually falls as it r' --^ on through the cylinder, 
which becomes larger in diameter as the exhaust end is 
approached. In other types of turbines, the steam is 
admitted to and directed against the blades or buckets, 
through expanding nozzles, and by the time it strikes the 
first stage, or section of moving vanes, the pressure has 
fallen to one-third or less of the original boiler-pressure, 
but the velocity is very great. 

Ques. 714. — In what particular respect does the steam 
turbine appear to possess an advantage over the recipro- 
cating engine, in the use of steam? 

Ans. — The turbine, if designed along correct lines, 
is capable of utilizing in the highest degree one of the 
most valuable properties of steam, viz., velocity. 

Ques. 715. — Give an example of the great increase in 
the amount of work performed by an agent when velocity 
is one of the factors made use of. 

Ans. — Suppose that a man is standing within arm's 



306 QUESTIONS AND ANSWERS 

length of a heavy plate-glass window and that he holds in 
his hand an iron ball weighing 10 pounds. Suppose the 
man should place the ball against the glass and press the 
same there with all the energy he is capable of exerting. 
He would make very little, if any, impression upon the 
glass. But suppose that he should walk away from the 
Iwindow a distance of 20 feet, and then exert the sam^e 
amount of energy in throwing the ball against the glass, 
a different result would ensue. The velocity with which 
the ball would impinge against the surface of the glass 
would no doubt ruin the window. Now, notwithstanding 
the fact that weight, energy, and time involved were 
exactly the same in both insicxxxces, yet a much larger 
amount of work was performed in the latter case, owing 
to the added force imparted to the ball by the velocity w4th 
which it impinged against the glass. 

Ques. 716. — Describe the construction and action of 
the De Laval steam turbine. 

Ans. — The De Laval steam turbine is termed by its 
builders a high-speed rotary steam-engine. It has but a 
single wheel, fitted with vanes or buckets of such curva- 
ture as has been found to be best adapted for receiving 
the impulse of the steam-jet. There are no stationary or 
guide-blades, the angular position of the nozzles giving 
direction to the jet. The nozzles are placed at an angle 
of 20 degrees to the plane of motion of the buckets. 
The heat energy in the steam is practically devoted to 
the production of velocity in the expanding or divergent 
nozzle, and the velocity thus attained by the issuing jet 
of steam is about 4,000 feet per second. To attain the 



STEAM TURBINE — FUNDAMENTAL PRINCIPLES 



307 



maximum of efficiency, t!ie buckets attached to the 
periphery of the wheel against which this jet impinges 
should have a speed of about 1,900 feet per second, but, 
owing to the difficulty of producing a material for the 
wheel strong enough to withstand the strains induced by 




Fig. 188. Thb De Lavai. Turbine Wheei* and Nozzi.es. 



such a high speed, it has been found necessary to limit 
the peripheral speed to 1,200 or 1,300 feet per second. 

Ques. 717. — Describe the action of the steam in its 
passage through the De Laval diverging nozzle, 

Ans. — It is well known that in a correctly designed 
nozzle the adiabatic expansion of the steam from max- 



308 



QUESTIONS AND ANSWERS 



imum to minimum pressure will convert the entire static 
energy of the steam into kinetic. Theoretically this is 
what occurs in the De Laval nozzle. The expanding steam 
acquires great velocity, and the energy of the jet of steam 




issuing from the nozzle is equal to the amount of energy 
that would be developed if an equal volume of steam were 
allowed to adiabatically expand behind the piston of a 
reciprocating engine, a condition, however, which for 
obvious reasons has never yet been attained in practice 



STEAM TURBINE FUNDAMENTAL PRINCIPLES 309 

With the reciprocating engine. But with the divergent 
nozzle the conditions are different. 

Ques. 718. — What is the usual speed of the De Laval 
steam-turbine wheel? 

Ans. — From 10,000 to 30,000 revolutions per minute, 
according to the size of the machine. 

Ques. 719. — How are the difficulties attending such 
high velocities overcome? 

Ans.— By the long, flexible shaft and the ball and 
socket type of bearings, which allow of a slight flexure 
of the shaft in order that the wheel may revolve about its 
center of gravity rather than the geometrical center or 
center of position. All high-speed parts of the machine 
are made of forged nickel steel of great tensile strength. 

Ques. 720. — How is the speed of the De Laval 
turbine-wheel and shaft reduced and transmitted for 
practical purposes? 

Ans. — By a pair of very perfectly cut spiral gears, 
usually made 10 to 1. These gear-wheels are made of 
solid cast steel, or of cast iron with steel rims pressed on. 
The teeth in two rows are set at an angle of 90 degrees to 
each other. This arrangement insures smooth running 
and at the same time checks any tendency of the shaft 
towards end-thrust, thus dispensing with a thrust bearing. 

Ques. 721. — How are the buckets made and fitted to 
the De Laval wheel? 

Ans.— The buckets are drop-forged and made with a 
bulb shank, fitted in slots, that are milled in the rim of 
the wheel. 

Ques. 722. — How many buckets are there? 



310 



QUESTIONS AND ANSWERS 



Ans. — The number of buckets varies according to the 
capacity of the machine. There are about 350 buckets 







CJ qj 3 



en M w 
'i 5 2 

Sen 



:3" 



bfl 



P3 M C 

i; oj to 

-o c o 



2.2-5 



a; 3T o 
P-i o « 






CO ^ 



■" > a 



on a 300 horse-power wheel which is the largest size built 
up to the present time. 



STEAM TURBINE FUNDAMENTAL PRINCIPLES 



311 



Ques. 723. — How many of the diverging nozzles are 
fitted to each wheel? 

Ans. — The number of these nozzles depends upon the 
size of the machine, ranging from one to fifteen. They 
are generally fitted with shut-off valves by which one or 
more nozzles can be cut out when the load is light. This 







^-y^' 



Fig. 191. Working Parts of the De lyAVAi, Steam Turbine. 



A.— Turbine shaft. 

B. — Turbine wheel. 

C. — Pinion. 

D. — Pinion bearing, two parts. 

K. — Pinion bearing, two parts. 

F. — Wheel bearing with spring. 

G. — Flexible bearing. 

H. — Gear wheel. 



I. — Gear wheel shaft. 

J. — Gear wheel bearing, two parts. 
K.— Oil ring. 

L. — Gear wheel bearing in position. 
M. — Coupling. 
N. — Centrifugal governor. 

O. — Gland adjusting nut. 

P.— Adjusting nut for flexible bearing 



renders it possible to use steam at boiler-pressure, no 
matter how small the volume required for the load. This 
is a matter of great importance, especially where the load 
varies considerably, as, for instance, there are plants in 
which during certain hours of the day a 300 horse-power 
machine may be taxed to its utmost capacity and duringf 



313 QUESTIONS AND ANSWERS 

certain other hours the load on the same machine may 
drop to 50 horse-power. In such cases the number of 
nozzles in action may be reduced by closing the shut-off 
valves until the required volume of steam is admitted to 
the wheel. This adds to the economy of the machine. 
After passing through the nozzles, the steam, as elsewhere 
explained, is now comipletely expanded, and in impinging 
on the buckets its kinetic energy is transferred to the 
turbine wheel. Leaving the buckets, the steam now 
passes into the exhaust-chamber, and out through the 
exhaust-opening, to the condenser or atmosphere, as the 
case may be. 

Ques. 724. — -How is the speed of this turbine regu- 
lated.^ 

Ans. — The governor is of the centrifugal type, 
although differing greatly in detail from the ordinary 
fly-ball governor. It is connected directly to the end of 
the gear-wheel shaft. 

Ques. 725. — Describe the methods of lubricating the 
bearings on the De Laval turbine. 

Ans. — The main shaft and dynamo bearings are ring- 
oiling. The high-speed bearings on the turbine shaft are 
fed by gravity from an oil-reservoir, and the drip-oil is 
collected in the base and may be filtered and used again. 

Ques. 726. — What can be said regarding the steam- 
consumption of this turbine? 

Ans.— Efficiency tests of the De Laval turbine show 
a high economy in steam-consumption, as, for instance, a 
test made by Messrs. Dean and Main, of Boston, Mass., 
on a 300 horse-power turbine, using saturated steam at 



STEAM TURBINE FUNDAMENTAL PRINCIPLES 



313 



about 200 pounds pressure per square inch and develop- 
ing 333 brake horse-power, showed a steam-consumption 
of 15.17 pounds per brake horse-power, and the same 
machine, when supplied with superheated steam and 
carrying a load of 352 brake horse-power, consumed but 







i 
1 


< 






1 ^ 






1. 



t4- 




Fig. 192. The De IvAval Steam Turbine Governor. 

Two* weights B are pivoted on knife edges A with hardened pins C. bearing 
on the spring seat D. K is the governor body fitted in the end of the gear wheel 
shaft K and has seats milled for the knife edges A. It is afterwards reduced in 
diameter to pass inside of the weights and its outer end is threaded to receive 
the adjusting nut I. by means of which the tension of the spring, and through 
this the speed of the turbine, is adjusted. When the speed accelerates, the 
weights, affected by centrifugal force, tend to spread apart, and pressing on the 
spring seat at D push the governor pin G to the right, thus actuating the bell 
crank L and cutting off a part of tha flow of steam. 



13.94 pounds per brake horse-power. These results 
compare most favorably with those of the highest type of 
reciprocating engines. 

Ques. 727. — Since the steam is used in but a single 



314 



QUESTIONS AND ANSWERS 



stage or section of buckets in the De Laval turbine, why 
such good economy in the use of steam? 

Ans. — The static energy in the steam as it enters the 
nozzles is converted into kinetic energy by its passage 
through the divergent nozzles, and the result is a greatly 
increased volume of steam leaving the nozzles at a tre- 
mendous velocity, but at a greatly reduced pressure- — 
practically exhaust pressure — impinging against the 
buckets of the turbine wheel and thus causing it to 
revolve. 

Table No. 11 
Capacities and Speed of De Laval Turbines 



Horse Power. 


Revolutions 
Turbine Shaft. 


Revolutions 
Main Shaft. 


Approximate 
Weight, 
Pounds. 


5 

10 
20 
75 

110 
225 

300 


30,000 
24,000 
20,000 
16,400 
13,000 
- 11,060 
10,500 


3,000 

2,400 
2,000 
1,500 
1,200 
900 
900 


330 

650 

1,250 

5,000 

8,000 

15,000 

20,000 



Ques. 728. — Describe in general terms the Curtis 
steam-turbine. 

Ans. — The Curtis turbine is built by the General 
Electric Company at their works in Schenectady, N. Y., 
and Lynn, Mass. The larger sizes are of the vertical 
type, and those of small capacity are horizontal. In the 
vertical t^^pe the revolving parts are set upon a vertical 
chaft, the diameter of the shaft corresponding to the size 
'i the machine. The shaft is supported by and runs 
upon a step-bearing at the bottom. This step-bearing 



STEAM TURBINE FUNDAMENTAL PRINCIPLES 



315 



consists of two cylindrical cast-iron plates bearing upon 
each other and having a central recess between them into 
which lubricating oil is forced under pressure by a steam 
or electrically driven pump, the oil passing up from 



Tff4MWM^'''-W^ 




Fig. 193. 5,000 K. W. Curtis Steam Turbine Direct Connected to 5,000 
K. W. Three-phase Aeternating Current Generator. 



beneath. A weighted accumulator is sometimes installed 
in connection with the oil pipe as a convenient device for 
governing the step-bearing pumps, and also as a safety 
device in case the pumps should fail, but it is seldom 
required f^r the htter purpose, as the step-bearing pumos 



316 QUESTIONS AND ANSWERS 

have proven, after a long service in a number of cases, 
to be reliable. The vertical shaft is also held in place and 
kept steady by three sleeve bearings, one just above the ^ 
step, one between the turbine and generator, and the f 
other near the top. These guide bearings are lubricated |i 
by a standard gravity feed system. It is apparent that 
the amount of friction in the machine is very small, and 
as there is no end-thrust caused by the action of the 
steam, the relation between the revolving and stationary 
blades may be maintained accurately. As a consequence, 
therefore, the clearances are reduced to the minimum. 
The Curtis turbine is divided into two or more stages, 
and each stage has one, two or more sets of revolving 
blades bolted upon the peripheries of wheels keyed to the 
shaft. There are also the corresponding sets of station- 
ary blades, bolted to the inner v/alls of the cylinder or 
casing. 

Ques. 729. — What is the diameter of the vertical shaft 
for a 5,000 kilowatt turbine and dynamo? 

Ans. — Fourteen inches. 

Ques. 730. — How is the heat energy in the steam 
imparted to the wheel of the Curtis turbine? 

Ans. — Both by impulse and reaction. The steam is 
admitted through expanding nozzles in which nearly all of 
the expansive force of the steam is transformed into the 
force of velocity. The steam is caused to pass through 
one, two, or more stages of moving elements, each stage 
having its own set of expanding nozzles, each succeeding 
set of nozzles being greater in number and of larger area 
than the preceding set. The ratio of expansion within 



STEAM TURBINE FUNDAMENTAL PRINCIPLES 



317 



these nozzles depends upon the number of stages, as, for 
instance, in a two-stage machine the steam enters the 
initial set of nozzles at boiler-pressure, say 180 pounds. 
It leaves these nozzles and enters the first set of moving 
blades at a pressure of about 15 pounds, from which it 
further expands to atmospheric pressure in passing 




Fig. 194. One Stage of a 500 K. ^\ Lt rtis Steam Turbine in Course op 
Construction. 



through the wheels and intermediates. From the pres- 
sure in the first stage the steam again expands through 
the larger area of the second stage nozzles to a pressure 
slightly greater than the condenser vacuum at the 
entrance to the second set of moving blades, against 
which it now impinges and passes through, still doing 
work, due to velocity and mass. From this stage the 



318 



QUESTIONS AND ANSWERS 



Steam passes to the condenser. If the turbine is a four- 
stage machine and the initial pressure is 180 pounds, the 
pressure at the different stages would be distributed in 



StZG<3r-r-> ^/->&st. 










♦ 



\ 



/Veyzz^ JD/ar/D^fncrg^n 




AfQVTTf^ J3/GtC/GS 



/3/QC/&S 



CCOrCCGTCCCCCCCCCCCC 



A^Gv/n^ jS/q</gs 



JQ/csc/g^ 



'/1^3 v'/3r>gt/3/<GrG^G 3 






I I I 



Fig. 195. 



Diagram of the nozzles, moving blades and stationary blades of a two-stag 
Curtis steam turbine. The steam enters the nozzle openings at the top, controlled 
by the valves shown, two of the valves are open, and the course of the steam 
through the first stage is indicated by the arrows. 

about the following manner: Initial pressure, 180 
pounds; first stage^ 50 pounds: second stage, 5 pounds: 



STEAM TURBINE FUNDAMENTAL PRINCIPLES 319 

third stage, partial vacuum, and fourth stage, condenser 
vacuum. 

Ques. 731. — What are the diameters of the wheels? 

Ans. — The diameters of the wheels vary according to 
the size of the machine, that of a 5,000 kilowatt unit being 
13 feet. 

Ques. 732. — What amount of clearance is there be- 
tween the revolving and stationary blades? 

Ans. — -The clearance between the revolving and sta- 
tionary blades is from sV to tV inch, thus reducing the 
wastage of steam to a very low percentage. 

Ques. 733.— Describe the action of the steam in a 
two-stage Curtis turbine. 

Ans. — The steam enters the nozzle openings at the top 
through valves that are controlled by the governor. 
After passing successively through the different sets of 
moving blades and stationary blades in the first stage, the 
steam passes into the second steam-chest. The flow oi 
steam from this chamber to the second stage of buckets 
is also controlled by valves, but the function of these 
valves is not in the line of speed-regulation, but for the 
purpose of limiting the pressure in the stage-chambers, 
in a manner somewhat similar to the control of the 
receiver pressure in a two-cylinder or three-cylinder 
compound reciprocating engine. The valves controlling 
the admission of steam to the second and later stages 
differ from those in the first group in that they partake 
more of the nature of slide-valves and may be operated 
either by hand or automatically; in fact, they require but 
very little regulation, as the governing is always done by 



320 



QUESTIONS AND ANSWERS 



the live-Steam admission-valves. As previously stated, 
the steam first strikes the moving blades in the first stage 
of a two-stage machine at a pressure of about 15 pounds 




Fig. 196. Governor for 5,000 K. W. Turbine. 



above atmospheric pressure, but with great velocity. 
From this wheel it passes to the set of stationary blades 
between it and the next lower wheel. These stationary 
Mades chans^e the direction of fiow of the steam and cause 



STEAM TURBINE FUNDAMENTAL PRINCIPLES 321 

it to impinge against the buckets of the second wheel at 
the proper angle. 

Ques. 734. — How is speed-regulation accomplished in 
the Curtis steam turbine? 

Ans. — The governing of speed is accomplished in the 
first set of nozzles, and the control of the admission-valves 
here is effected by means of a centrifugal governor 
attached to the top end of the shaft. This governor, by 




Fig. 197. Electrically Operated Valve. 

la very slight movement, imparts motion to levers, which 
in turn work the valve mechanism. The admission of 
steam to the nozzles is controlled by piston-valves which 
are actuated by steam from small pilot-valves which are 
in turn under the control of the governor. Speed-regu- 
lation is effected by varying the number of nozzles in 
flow, that is, for light loads fewer nozzles are open and a 
smaller volume of steam is admitted to the turbine wheel, 
l^ut the steam that is admitted impinges against the mov 



n 



322 



QUESTIONS AND ANSWERS 



ing blades with the same velocity always, nz matter whether 
the volume be large or small. With a full load and all 
the nozzle sections in flow, ihe steam passes to the wheel 
in a broad belt and steady flow. 




Fig. 198. 5.000 Kii^owatt Generating Units. 

Comparison of space occupied and size of foundations. Modern Engine 
Type Unit and a Westinghouse-Parsons Turbine Type Unit of similar rating 
and overload capacity. 

Ques. 735. — What great advantage does the steam- 
turbine as a prime mover for an electric generator 
possess over the reciprocating engine? 

AH'?. — The advantage of a high soeed of revolutioiu 



STEAM TURBINE — FUNDAMENTAL PRINCIPLES 323 

whereby there can be a great reduction in the size; 
weight, and cost of the direct-driven generator. 

Ques. 736. — Give approximately the over-all dimen- 
sions of a Westinghouse-Parsons turbo-generator unit of 
5,500-kilowatt, 11,000 volt capacity, of the revolving field 
type, speed 750 revolutions per minute, vacuum to be 
27>^ inches. 

Ans.— Length 47 feet, width 13 feet, and height 
14 feet to top of gallery-ring. 




Fig. 199. Generai. View oe a 400 K. W. Turbine Generator Unit. 

Ques. 737. — What amount of floor-space would a 
reciprocating engine and direct-connected generator of 
equal capacity with the above occupy? 

Ans. — The generator would be 43 feet in extreme 
diameter, its weight would be 445 tons (speed to be 75 
revolutions per minute) and it, together with the four- 
cylinder piston engine, would fill a space 40 feet wide by 
60 feet long, and tower 45 feet in height. 

Ques. 738. — Describe in general terms the construe- 



324 QUESTIONS AND ANSWERS 

tion and principles of operation of the Westinghouse- 
Parsons steam-turbine. 

Ans. — The Westinghouse-Parsons steam-turbine is 
fundamentally based upon the invention of Mr. Charles 
A. Parsons, who, while experimenting with a reaction 
turbine constructed along the ll:'':s of Hero's engine, con- 
ceived the idea of combining the two principles, reaction 




Fig. 200. Shows a 600 H. P. machine with the upper half of the cylinder, or 
stator as it is termed, thrown back for inspection. 

and impulse, and also of causing the steam to flow in a 
general direction parallel with the shaft of the turbine. 
This principle of parallel flow is common to all four types 
of turbines, but is perhaps more prominent in the 
Westinghouse-Parsons and less so in the De Laval. The 
cylinder, or stator, as it is termed, is divided longitudinally 
into an upper and a lower half flanged and bolted together. 
There are three sections or drums, gradually increasing 



STEAM TURBINE FUNDAMENTAL PRINCIPLES 325 

in diameter from the inlet to the third and last group of 
blades. This arrangement may be likened in some 
measure to the triple-compound reciprocating engine. 

Ques. 739. — Describe the arrangement of the blades 
or buckets in the Westinghouse-Parsons steam-turbine. 

Ans. — There are two kinds of blades, viz., stationary 
blades and moving blades, but they are similar in shape, 
being of the same curvature. These blades are made of 
hard drawn material, and are set into their places and 
secured by a caulking process. The stationary blades 
project from the inside surface of the cylinder, while 
similar rows of moving blades project from the surface 
of the rotor, or revolving drum. When the upper half 
of the cylinder is in position each row of stationary blades 
fits in between two corresponding rows of moving blades. 

Ques. 740. — Are these blades all of the same length? 

Ans. — They are not. The length varies from Yz inch 
for the shortest to 7 inches for the longest, according to 
their location. The shortest blades are placed at the 
steam end of each section and the longest blades are 
placed at the opposite end. 

Ques. 741. — What is the clearance between the blades 
as they stand in the rows? 

Ans. — The clearance between the blades as they stand 
in the rows is Y^ inch for the smallest size blades and /^ 
inch for the larger ones, gradually increasing from the 
inlet to the exhaust. In the 5,000 kilowatt machine the 
clearance at the exhaust end between the rows of blades 
is 1 inch. 

Ques. 742. — What is the general direction taken by 



326 QUESTIONS AND ANSWERS 

the steam in its passage through the Westinghouse-Par- 
sons turbine? 

Ans. — The steam entering at the smaller end of the 
cylinder presses first against the shortest blades and then 
passes on through in the form of spiral or screw line about 
the rotor, continually pressing against new and gradually 
lengthening blades, thus doing work by reason of its 
velocity. 

1 1 C^ ^ ^ C C C.C C C STATIOHlARY BLADES 

J J) i) ^Kl) )) )) )) h »'N^ »^«K8 



CCCCCC^CC 



stationKry blades, 



}])}))]) :}))))¥ 



^ 



MOVING BLADES 



Fig. 201. SKCTiONAt View op Four Rows o^ Bi^ades, op a Westinghouse- 
Parsons Turbine. 

Ques. 743. — As steam presses equally in all directions, 
is there not a very heavy end-thrust exerted by the rotor? 

Ans. — There is not. The pressure in either direc- 
tion is perfectly balanced by means of balancing pistons 
placed on the steam end of the rotor. The diameters of 
these pistons correspond to the diameters of the different 
drums or sections."^ 

Ques. 744. — About what is the velocity of the steam 
in the Parsons turbine? 



*The theory and action of these balancing pistons is fully 
and completely described in Swingle's "Twentieth Century Hand 
Bock for Engineers and Electricians." 



STEAM TURBINE FUNDAMENTAL PRINCIPLES 327 

Ans. — The highest velocity does not exceed 600 feet a 
second. 

Ques. 745.— About what amount of pressure is 
exerted upon each blade by the steam? 

Ans. — The steam-thrust on each blade is said to be 
equal to about 1 ounce avoirdupois. 

Ques. 114:6. — With such a very light pressure upon 



il^ffV 





FiGo 202. SECTIONAL View o? a Westtnghouse-Parsons Turbine, Showing 
Arrangement o? Bai^ancing Pistons P. P. P. 



each blade, why is it that this turbine is capable of devel- 
oping power? 

Ans. — Because of the large number of blades; as, for 
instance, taking a 400 kilowatt machine, there are 1G,095 
moving blades and 14,978 stationary blades, a total of 
31,073. 

Ques. 747. — How are the clearances preserved? 

Ans. — ^A rigid shaft and thrust or adjustment bearing 
accurately preserves the clearances. 



328 QUESTIONS AND ANSWERS 

Ques. 748. — Describe the construction and action of 
the bearings. 

Ans. — The bearings are constructed along lines differ- 
ing from those of the ordinary i ^'ciprocating engine. The 
bearing proper is a gun-metal sleeve that is prevented 
from turning by a loose-fitting dowell. Outside of this 
sleeve are three concentric tubes having a small clearance 
between them. This clearance is kept constantly filled 
with oil supplied under light pressure, which permits a 
vibration of the inner shell or sleeve and at the same time 
tends to restrain or cushion it. This arrangement allows 
the shaft to revolve about its axis of gravity instead of 
the geometrical axis, as would be the case if the bearing 
were of the ordinary construction. The journal is thus 
to a certain degree a floating journal, free to run slightly 
eccentric according as the shaft may happen to be out of 
balance. 

Ques. 749. — How is the power of the Westinghouse- 
Parsons turbine transmitted to the dynamo, or other 
machine to be run? 

Ans. — A flexible coupling is provided, by means of 
which the power of the turbine is transmitted to the 
dynamo ^^ other machine it is intended to run. The oil 
from all the bearings drains back into a reservoir, and 
from there it is forced up into a chamber, where is forms 
a static head, which gives a constant pressure of oil on 
all the bearings. 

Ques. 750. — How is the speed governed? 

Ans. — The speed of the Westinghouse-Parsons 
turbine is regulated by a fly-ball governer constructed in 



STEAM TURBINE— FUNDAMENTAL PRINCIPLES 



329 



such manner that a very slight movement of the balls 
serves to produce the required change in the supply of 
steam. The ball levers swing on knife edges instead of 
pins. The governor works both ways, that is to say, 
when the levers are oscillating about their mid position a 
head of steam corresponding to full load is being admitted 
to the turbine, and a movement from this point, either up 
or down, tends to increase or to decrease the supply of 
steam. 




Fig. 203. Section op Westinghouse-Parsons Turbine Governor. 



Ques. 751. — What can be said of the efficiency of the 
Westinghouse-Parsons steam-turbine? 

Ans. — Under test a 400 kilowatt Westinghouse-Par- 
sons steam-turbine, using steam at 150 pounds initial 
pressure and superheated about 180 degrees, consumed 
11.17 pounds of steam per brake horse-power hour at full 
load. The speed was 3,550 revolutions per minute and 
the vacuum was 28 inches. With dry saturated steam 



330 QUESTIONS AND ANSWERS 

the consumption was 13.5 pounds per brake horse-power 
hour at full load, and 15.5 pounds at one-half load. A 
1,000 kilowatt machine, using steam of 150 pounds pres- 
sure and superheated 140 degrees, exhausting into a 
vacuum of 28 inches, showed the very remarkable 
jeconomy of 12.66 pounds of steam per electrical horse- 
power per hour. A 1,500 kilowatt Westinghouse-Par- 
son turbine, using dry saturated steam of 150 pounds 
pressure with 27 inches vacuum, consumed 14.8 pounds 
steam per electrical horse-power hour at full load, and 
17.2 pounds at one-half load. 

Ques. 752. — What efficiency does the Curtis turbine 
show in the use of steam? 

Ans.— A 600 kilowatt Curtis turbine operating at 
1,50P revolutions per minute, with steam at 140 pounds 
gaugfc-pressure and 28.5 inches vacuum, showed a steam- 
consumption as follows, steam superheated 150 degrees: 
At full load, 12.5 pounds per electrical horse-power per 
hour; at half load, 13.25 pounds per electrical horse-power 
per hour; at one-sixth load, 16.2 pounds per electrical 
horse-power per hour, and at one-third overload, 12.4 
pounds per electrical horse-power per hour. 
( Ques. 753. — Describe in brief terms the Hamilton- 
Holzwarth steam-turbine. 

Ans. — The Hamilton-Holzwarth steam-turbine is 
based upon and has been developed from the designs of 
Prof. Rateau, and is being manufactured in this country 
by the Hooven-Owens-Rentschler Company, of Hamilton, 
Ohio. It is horizontal and placed upon a rigid bed-plate 
of the box pattern. All steam, oil and water-pipes are 



STEAM TURBINE FUNDAMENTAL PRINCIPLES 331 

within and beneath this bed-plate, as are also the steam- 
inlet-valve and the regulating and by-pass valves. The 
smaller sizes of this turbine are built in a single casing or 
cylinder, but for units of 750 kilowatts and larger the 
revolving element is divided into two parts, high and low 
pressure. This turbine resembles the Westinghouse-Par- 
sons turbine in some respects, prominent of which is that 
it is a full-stroke turbine, that is, that the steam flows 
through it in one continuous belt or veil in screw line, 
the general direction being parallel with the shaft. But, 
unlike the Parsons type, the steam in the Hamilton-Holz- 
warth turbine is made to do its work only by impulse, 
and not by impulse and reaction combined. It might 
thus be termed an action turbine. 

Ques. 754. — Describe the interior construction of this 
turbine. 

Ans. — The interior of the cylinder is divided into a 
series of stages by stationary disks which are set in 
grooves in the cylinder and are bored in the center to 
allow the shaft, or rather the hubs of the running wheels 
that are keyed to the shaft, to revolve in this bore. 
There are no balancing pistons in this machine, the axial 
thrust of the shaft being taken up by a thrust ball-bear- 
ing. Between each two stationary disks there is located 
a running wheel, and the clearance between the running, 
vanes and the stationary vanes is made as slight as is' 
consistent with safe practice. 

Ques. 755. — Describe the construction of the running 
\anes and the action of the steam upon them. 

Ans. — The running vanes conform in section somewhat 



332 



QUESTIONS AND ANSWERS 



to the Parsons type, but the action of the steam upon 
them and also within the stationary vanes is different. The 
expansion of the steam and 
consequent development of 
velocity takes place entirely 
within the stationary vanes, 
which also change the direc- 
tion of flow of the steam and 
distribute it in the proper 
manner to the vanes of the 
running wheels, which, ac- 
cording to the claims of the 
makers, the steam enters 
and leaves at the same pres- 
sure, thus allowing the 
wheel to revolve in a uni- 
form pressure. 

Ques. 756.— What pro- 
vision is made in the Hamil- 
ton-Holzwarth turbine for 
maintaining the velocity of 
the steam as it expands? 

Ans. — The first station- 
ary disk of the low-pressure 
turbine has guide-vanes all 
around its circumference, 
so that the steam enters the 
turbine in a full cylindrical belt, interrupted only by the 
guide-vanes. To provide for the increasing volume as 
the steam expands in its course through the turbine, the 




STEAM TURBINE FUNDAMENTAL PRINCIPLES 333 

areas of the passages through the distributers and running 
vanes must be progressively enlarged. The gradual in- 
crease in the dimensions of the stationary vanes permits 
the steam to expand within them, thus tending to maintain 
its velocity, while at the same time the vanes guide the 
steam under such a small angle that the force with which 
it impinges against the vanes of the next running wheel 
is as effective as possible. The curvature of the vanes is 
such that the steam while passing through them will in- 
crease its velocity in a ratio corresponding to its oper- 
ation. 

Ques. 757. — Describe the method of regulating the 
speed of this turbine. 

Ans.— The governor is of the spring and weight type, 
adapted to high speed, and is designed especially for 
turbine governing. It is directly driven by the turbine- 
shaft, revolving with the same angular velocity. Its action 
is as follows: Two disks keyed to the shaft, drive, by 
means of rollers, two weights sliding along a cross-bar 
placed at right angles through the shaft and compressing 
two springs against two nuts on the cross-bar. Every 
movement of the weights, caused by increasing or decreas- 
ing the angular velocity of the turbine-shaft, is trans- 
mitted by means of levers to a sleeve which actuates the 
regulating mechanism. These levers are balanced so that 
no back pressure is exerted upon the weights. The whole 
governor is closed in by the disks, one on each side, and a 
steel ring secured by concentric recesses to the disks. In 
order to decrease the friction within the governor and 
regulating mechanism, thrust ball-bearings and friction- 
less roller-bearings are used. 



334 QUESTIONS AND ANSWERS 

Ques. 758. — Describe the action of the steam within 
th3 Hamilton-Holzwarth steam-turbine. 

Ans. — After leaving the steam-separator that is 
located beneath the bed-plate, the steam passes through 
the inlet or throttle-valve, the stem of which extends up 
through the floor near the high-pressure casing and is 
protected by a floor-stand and equipped with a hand 
wheel. The steam now passes through the regulating 
valve, which will be described later on. From this valve 
it is led through a curved pipe to the front head of the 
high-pressure casing or cylinder. In this head is a ring 
channel into which the steam enters, and from whence it 
flows through the first set of stationary vanes. 

Ques. 759. — Describe the action of the steam as it 
passes through the first set of stationary vanes. 

Ans. — In these vanes the iirst stage of expansion 
occurs, the velocity of the flow is accelerated, and the 
direction of flow is changed by the curve of the vanes in 
such manner that the steam impinges against the vanes 
of the first running wheel at the proper angle and in a full 
cylindrical belt, imparting by impulse a portion of its 
energy <"o the wheel. }l 

Ques. 760. — What takes place in the course of the 
steam after leaving the first running wheel? 

Ans. — Passing through the vanes of this wheel, the 
steam immediately enters the vanes of the second station- 
ary disk, which are larger in area than those of the first, I 
and here occurs the second stage of expansion, another 
acceleration of velocity, and also the proper change in 
direction, and the steam leaves this distributer and 



STEAM TURBINE FUNDAMENTAL PRINCIPLES 335 

impinges against the vanes of the second running wheel. 
This cycle is repeated throughout the several stages of 
the turbine, a certain percentage of the heat energy in the 
steam being imparted by impulse to each wheel and thence 
to the turbine-shaft. From the last running wheel the 
steam is led through receiver pipes to the front head of 
the low-pressure cylinder, or, if there is but one cylinder, 
directly to the condenser or the atmosphere. 

Ques. 761. — Describe the construction and location 
of the regulating valve. 

Ans. — The regulating valve is located beneath the 
bed-plate. One side of it is connected by a curved pipe 
with the front head of the high-pressure cylinder and the 
other side is connected with the inlet-valve. The regulat- 
ing valve is of the double-seated poppet-valve type. 
Valves and valve-seats are made of tough cast steel, to 
avoid corrosion as much as possible, and the valve-body 
is made of cast iron. 

Ques. 762. — Describe the by-pass regulating valve. 

Ans. — This valve is also a double-seated poppet-valve 
and is located immediately below the regulating valve and 
forming a part of it. Thus the use of a second stuffing 
box for the stem of this valve is avoided. The function 
of this valve is to control the volume of the live-steam 
supply that flows directly to the by-pass nozzles in the 
front head of the low-pressure casing. 

Ques, 763. — How is the main regulating valve 
operated? 

Ans. — The main regulating valve is not actuated 
directly by the governor, but by means of the regulating 
mechanism. 



336 QUESTIONS AND ANSWERS 

Ques. 764. — Describe the construction and operation 
of the regulating mechanism of the Hamilton-Holzwarth 
steam-turbines. 

Ans. — The construction and operation of this regulat- 
ing mechanism is as follows: The stem of the regulating 
valve is driven by means of bevel gears by a shaft that is 
supported in frictionless roller-bearings. On this shaft 
there is a friction wheel that the governor can slide across 
the face of a continuously revolving friction disk by 
means of its sleeve and bell-crank lever. This revolving 
disk is keyed to a solid shaft which is driven by a coupling 
from a hollow shaft. This hollow shaft is driven by the 
turbine-shaft through the medium of a worm gear. The 
solid shaft, with the continuously revolving friction disk, 
can be slightly shifted by the governor sleeve so that the 
two friction disks come into contact when the sleeve 
moves, that is, when the angular velocity changes. If 
this change is relativeh^ great, the sleeve will draw the 
periodically revolving friction disk far from the center of 
the always revolving one, and this disk will quickly drive 
the stem of the regulating valve and the flow of steam will 
thus be regulated. As soon as the angular velocity falls 
below a certain percentage of the normal speed, the 
driving friction disk is drawn back by the governor, the 
regulating valve remains open and the whole regulating 
mechanism rests or stops, although the shaft is still 
running. 

Ques. 765.— Under what conditions will this governor 
shut down the turbine? 

Ans. — Should the angular velocity of the shaft reach 



STEAM TURBINE^ — FUNDAMENTAL PRINCIPLES 337 

a point 2.5 per cent higher than normal, the governor will 
shut down the turbine. If an accident should happen to 
the governor, due to imperfect material or breaking or 
weakening of the springs, the result would be a shut- 
down of the turbine. 

Ques. 766. — How may the speed of this turbine be 
changed, while running, if necessary? 

Ans. — In order to change the speed of the turbine 
while running, which might be necessary in order to run 
the machine parallel with another prime mover, a spring 
balance is provided, attached to the bell-crank lever of 
the regulating mechanism. The hand-wheel of this spring 
balance is outside of the pedestal for regulating mechanism 
and near the floor-stand and hand-wheel. With this 
spring balance the speed of the turbine may be changed 
5 per cent either way from normal. 

Ques. 767. — What is the best method of disposing of 
the exhaust steam of steam-turbines? 

Ans. — As in the case of the reciprocating engine, the 
highest efficiency in the operation of the steam-turbine is 
obtained by allowing the exhaust steam to pass into a 
condenser, and experience has demonstrated that it is 
possible to m.aintain a higher vacuum in the condenser of 
a turbine than in that of a reciprocating engine. This 
is due, no doubt, to the fact that in the turbine the steam 
is expanded down to a much lower pressure than is pos- 
sible with the reciprocating engine. 

Ques. 768. — What type of condensing apparatus is 
best adapted to steam-turbines? 

Ans. — The condensing apparatus used in connection 



338 QUESTIONS AND ANSWERS 

with steam-turbines may consist of any one of the 
modern improved systems, and as no cylinder-oil is usecf 
within the cylinder of the turbine, the water of condensa- 
tion may be returned to the boilers as feed-water. If the 
condensing water is foul or containj matter that would 
be injurious to the boilers, a surface condenser should be 
used. If the water of condensation is not to be used in 
the boilers, the jet system may be employed. 

Ques. 769. — What percentage of gain may be effected 
by allowing the exhaust steam from the turbine to pass 
into a good condenser? 

Ans. — As an instance of the great gain in economy 
effected by the use of the condenser in connection with 
the steam-turbine, a 750 kilowatt Westinghouse-Parsons 
turbine, using steam of 150 pounds pressure, not super- 
heated and exhausting into a vacuum of 28 inches, showed 
a steam consumption of 13.77 pounds per brake horse- 
power per hour, while the same machine operating non- 
condensing consumed 28.26 pounds of steam per brake 
horse-power hour. Practically the same percentage in 
economy effected by condensing the exhaust applies to 
the other types of steam-turbines. 

Ques. 770. — About what is the additional cost of 
operating a complete condensing outfit in connection 
with a steam-turbine plant? 

Ans. — With reference to the relative cost of operating 
the several auxiliaries necessary to a complete condensing 
outfit, the highest authorities on the subject place the 
power consumption of these auxiliaries at from 2 to 7 per 
cent of the total turbine output of power. A portion of 



STEAM TURBINE — FUNDAMENTAL PRINCIPLES 339 

this is regained by the use of an open heater for the feed- 
water, into which the exhaust steam from the auxiliaries 
may pass, thus heating the feed-water and returning a 
part of the heat to the boilers. 

Ques. 771. — What precautions must be observed in 
the operation of a condensing outfit in order to obtain the 
highest efficiency? 

Ans. — A prime requisite to the maintenance of high 
vacuum, with the resultant economy in the operation of 
the condensing apparatus, is that all entrained air must 
be excluded from the condenser. There are various ways 
in which it is possible for air to find its way into the con- 
densing system. For instance, there may be an improp- 
erly packed gland, or there may be slight leaks in the 
piping, or the air may be introduced with the condensing- 
water. This air should be removed before it reaches the 
condenser, and it may be accomplished by means of the 
**dry" air-pump. 

Ques. 772. — Describe some of the leading character- 
istics of the dry air-pump. 

Ans. — This dry air-pump is different from the 
ordinary air-pump that is used in connection with most 
I condensing systems. The dry air-pump handles no 
water, the cylinder being lubricated with oil in the same 
manner as the steam-cylinder. The clearances also are 
made as small as possible. These pumps are built either 
in one or two stages. 

Ques. 773. — What particular features would be 
required in the design of a compound or stage-expansion 
reciprocating engine, in order to develop a high vacuum, 
for instance as hieh as 28.5 inches? 



340 QUESTIONS AND ANSWERS 

Ans. — In comparing the efBciency of the reciprocating 
engine and the steam-turbine it is not to be inferred that 
reciprocating engines would not give better results at 
'high vacuum than they do at the usual rate of 25 to 26 
inches, but to reach and maintain the higher vacuum of 
38 to 28.5 inches with the reciprocating engine would 
necessitate much larger sizes of the low-pressure cylinder, 
as also the valves and exhaust pipes, in order to handle 
the greatly increased volume of steam at the low-pressure 
demanded by high vacuum. 

Ques. 774.— What advantage has the turbine over the 
reciprocating engine, in the disposal of its exhaust 
steam? 

Ans.— The steams-turbine expands its working steam 
to within 1 inch of the vacuum existing in the condenser, 
that is, if there is a vacuum of 28 inches in the condenser 
there will be 27 inches of vacuum in the exhaust end of 
the turbine cylinder. On the other hand, there is usually 
a diflference of 4 or o inches (2 to 2.5 pounds) between 
the mican back pressure in the cylinder of a reciprocating 
condensing engine and the absolute back pressure in the 
condenser. 

Ques. 775.— Mention the two principal sources of 
economy that the steam-turbine possesses in a high 
degree. 

Ans. — Two of the main sources of economy that the 
steam-turbine possesses in a much higher degree than 
does the reciprocating engine are: First, its adaptability 
for using superheated steam, and second, the possibility 
of maintaining a higher degree of vacuum. 




H 

S 






It* 



342 QUESTIONS AND ANSWERS 

Ques. 776.— What can be said of the steam turbine, 
regarding friction of rubbing parts, such as reciprocating 
pistons, cross-heads, etc? 

Ans. — There are no rubbing surfaces in the turbine 
except the bearings of the rotor. 

Ques. 777. — Of what type is the Allis Chalmers steam- 
turbine? 

Ans. — It is of the reaction, or Parsons type, with a 
number of modifications in details of construction. 

Ques. 778, — Give an elementary description of the 
**Parsons" steam-turbine. 

Ans. — It consists essentially of a fixed casing, or 
cylinder, usually arranged in three stages of different 
diameters, that of the smallest diameter being at the high- 
pressure, or admission end, and that of the largest diam- 
eter at the low-pressure or exhaust end of the casing. 

Inside of this casing is a revolving drum, or rotor, the 
ends of which are extended in the form of a shaft, and 
carried in two bearings, just outside each end of the cyl- 
inder. 

Ques» 779. — What causes the drum to revolve within 
the cylinder? 

Ans. — The drum is fitted with a large number of small 
curved blades, or paddles arranged in straight rows 
around its circumference. The blades in each stage, or 
step, are also arranged in groups of increasing length, 
those at the beginning of each larger stage being shorter 
than those at the end of the preceding stage, the change 
being made in such a manner that the correct relation of 
blade length to drum diameter is secured. These rows of 



STEAM TURBINE FUNDAMENTAL PRINCIPLES 



343 



revolving blades fit in and run between corresponding 
rows of stationary blades that project from the walls of 
the cylinder. These stationary blades have the same cur- 
vature as the revolving blades, but are set so that the 
curves incline in the opposite direction to those of the 
revolving blades. The steam entering the cylinder at the 
smallest or first stage, is deflected in its course by the 
first row of stationary blades, and immediately impinges 
with a pressure but slightly reduced from boiler pressure, 
against the first row of revolving blades. It then passes 




CLEHENTARri^RSaN6TYPE STEAM TURBINE 



Fig. 206. 

Main bearings, A and B. Thrust bearing, R. Steam pipe, C Main throttle 
valve, D, which is balanced, and operated by the governor. Steam enters the 
cylinder through passage E, passes to the left through the alternate rows of 
stationary and revolving blades, leaving the cylinder at F and passes into the 
condenser, or atmosphere through passage G. H, J and K are the three steps or 
stages of the machine. L, M and N are the three balance pistons. O, P and 
Q are the equalizing passages, connecting the balance pistons with the corres- 
ponding stages. 



to the next row of stationary blades, which again deflect 
its course so as to cause it to strike the next row of mov- 
ing blades at the proper angle. Thus the continual 
pressure and reaction of the steam against the cuivec? 
surfaces of the moving blades causes the drum, or rotor 
to revolve. 




Fig. 207, Spindle or Rotor, Ati,is Chalmers Steam Turbine. 
The rings which carry the blades are pressed OiL 



STEAM TURBINE FUNDAMENTAL PRINCIPLES 



345 



Ques. 780. — Does not the action of the steam against 
the revolving blades tend to produce a strong end thrust? 

Ans. — It does — but this thrust is neutralized by three 
**balance-pistons" so called, which are fitted upon the 
revolving drum at the high-pressure end of the cylinder. 
The diameter of each **piston" corresponds with the 
diameter of that stage of the cylinder with which it is 
connected by an equalizing passage which permits the 
steam to act upon it, and thus balance the thrust. 




Fig. 208. 

Fig. 208 showing arrangement of blading and course of the steam in Parsont 
Steam turbine. 



Ques. 781. — Do the revolving blades come in contact 
with the stationary parts? 

Ans. — They do not. The high speeds which are nec- 
essary in the steam turbine prohibit any continuous con- 



346 



QUESTIONS AND ANSWERS 



tact between moving and stationary parts, except in the 
lubricated bearings. 

Ques. 782. — How much clearance is allowed between 
the moving and stationary parts in the **Par sons'' steam- 
turbine? 

' Ans.— The tips of the revolving blades just clear the 
walls of the cylinder, and the tips of the stationary blades 
just clear the surface of the rotor. 




FIG.3 



Fig. 209. 



Sectional view of elementaTy Parsons steam turbine, with Allis ChalmerSv 
modifications. L and M are the two balance pistons at the high pressure end. 
Z is a smaller balance piston placed in the low pressure end, yet having the 
same effective area as did the larger piston N shown m Fig. 206. O and Q are 
the two equalizing passages for pistons L, and M. Passage P is omitted in this 
construction and balance piston Z is equalized with the third stage pressure at 
Y. Valve V is a by-pass valve to allow of live steam being admitted, to the 
secend stage of the cylinder in case of a sudden overload. This by-pass valve is 
the equivalent of the by-pass valve used to admit live steam to the low pressure 
cylinder of a compound reciprocating engine. Valve V is arranged to be 
operated, either by the governor or by hand, as the conditions may require. 
Frictionless glands made tight by water packing are provided at S and T where 
the shaft passes out of the cylinder. The shaft is extended at U and connected 
to the generator shaft by a flexible coupling. 



Ques„ 783. — How are the clearances between the 
edges of the revolving and stationary blades preserved? 

Ans. — The position of the drum, as regards end play, 
is definitely fixed by means of a small ^'thrust bearing" 
provided inside the housing of the main bearing. 

This so-called thrust bearing can be adjusted to locate. 



STEAM TURBINE FUNDAMENTAL PRINCIPLES 347 

and hold the revolving spindle or rotor in such position as 
will allow sufficient clearance between the moving and 
stationary blades, and yet reduce the leakage of steam to 
a minimum. 

Ques. 784. — Is there not danger of out leakage of 
steam, and in leakage of air, where the shaft passes out 
of the high and low-pressure ends of the cylinder? 

Ans. — There is; but this is provided for by glands 
that are made practically frictionless by water packing, 
without metallic contact. 

Ques. 785. — How is the power of the *'Parsons" type 
of steam-turbine transmitted to the electric generator, or 
other machine to be run? 

Ans. — ^The shaft is extended at the low-pressure end, 
and coupled to the shaft of the generator by means of a 
flexible coupling. 

Ques. 786. — What provision is made in this type of 
steam-turbine for speed regulation? 

Ans. — The speed of the **Parsons'' turbine is regu- 
lated by a very sensitive governor driven from the turbine 
shaft by means of cut gears working in an oil bath. The 
governor operates a balanced throttle-valve, and may be 
adjusted for speed while the turbine is in motion if 
necessary for the synchronizing of alternators, and divid-j 
ing the load. 

Ques. 787. — Suppose there should be an accidental 
derangement of the governing mechanism, what provision 
is made for preventing dangerous over speed? 

Ans. — A separate safety governor is provided, driven 
directly by the turbine shaft, without the intervention of 



348 QUESTIONS AND ANSWERS 

gearing, and so adjusted that if the speed of the turbine 
should reach a predetermined point above that for which 
the main governor is set, the satcjj governor will come 
into action, and trip a valve, thus shutting off the steam, 
and stopping the turbine. 

Ques. 788. — Is the arrangement of * 'balance-pistons" 
described in answer to question 780 carried out in all 
sizes of steam-turbines of the *'Parsons" type? 

Ans. — No. In the larger sizes of the Allis Chalmers 
steam-turbine, the largest one of the three pistons at the 
high-pressure end is replaced by a smaller balance-piston 
located at the low-pressure end of the turbine, and work- 
ing inside a supplementary cylinder. 

This piston presents the same effective area for the 
steam to act upon, as did the larger piston, because the 
working area of the latter in its original location con- 
sisted only of the annular area included between its 
periphery, and the periphery of the next smaller piston. 

Ques. 789. — How is the pressure of the steam brought 
to bear upon this equalizing piston in its new position? 

Ans. — By means of passages through the body of the 
rotor, connecting the third stage of the cylinder with 
the supplementary cylinder in which the piston revolves. 

Ques. 790. — How are the blades or paddles fitted to, 
and held in the rotor, and c^dinder of the Allis Chalmers 
steam-turbine? 

Ans. — Each blade is individually formed by special 
machine tools, so that its root or foot is of an angular 
dove-tail shape, and at its tip there is a projection. 

Foundation rings are provided for each row of blades. 



350 QUESTIONS AND ANSWERS 

These rin^s have slots of dove-tail shape cut into them 
to receive the roots of the blades. These slots are accu- 
rately spaced, and inclined so as to give the required 
pitch and angle to the blades. The foundation rings 
themselves are dove-tail in cross section, and are inserted 
in dove-tail grooves cut in the turbine cylinder, and rotor 
respectively. These rings are firmly held in place by key 
pieces that are driven into place, and upset into undercut 
grooves, thus locking the whole structure firmly together. 

Ques. 791. — How are the tips or outer ends of the 
blades protected? 

Ans. — By a shroud ring for each row, in which holes 
are punched to receive the projections on the tips of the 
blades. 

These holes are spaced by special machinery to match 
the slots in the foundation ring. 

Ques. 792. — Describe the construction of the shroud 
rings. 

Ans. — They are channel shaped in cross section, and 
are made thin, so that in case of accidental contact with 
an opposing surface no dangerous heating will occur, 
neither will the rubbing be so liable to rip out the blades, 
as it is when they are unprotected by a shroud ring. 

Ques. 793. — Mention another advantage in connection 
with the use of a shroud ring. 

Ans. — The blades in each row are stiflfened, and hela. 
together as a unit by its use, thus permitting smaller 
clearances, and reducing the leakage loss to a minimum. 
The channel shape of the shroud ring also forms an 
eflfective baffle to the steam leakagre. 




Fig. 211. 

Fig. 211 illustrates blades as fitted in the rotor of Allis Chalmers steam 
turbine. The shroud rin« protecting the tips of the blades is also shown. 



353 



QUESTIONS AND ANSWERS 



Ques. 794. — What type of bearings are the AUis 
Chalmers steam-turbines fitted with? 

Ans. — Self-adjusting ball and socket bearings espe- 
cially designed for high speed, shims being provided for 
proper alignment. 




Fig. 212. 

Fig. 212 shows a number of rows of stationary blades fitted in the cylinder of 
an Allis Chalmers steam turbine. 

In the smaller sizes the bearing shells are made of 
special bronze, and in the larger sizes white metal is used 
for bearing surface. 



STEAM TURBINE — FUNDAMENTAL PRINCIPLES 353 

Ques. 795. — How are these bearings lubricated? 

Ans. — The oil is supplied freely to the middle of each 
bearing, and allowed to flow out at the ends, where it is 
caught, passed through a cooler, and pumped back to the 
bearings, to be used again and again. 

Ques. 796. — Does the fact that the oil is supplied 
to the bearings in large quantities necessarily imply a 
heavy expenditure for oil? 

Ans. — It does not; for the reason that the bearings 
practically float on oil films, thus preventing that *Vear- 
ing out^' of the oil which occurs when it is supplied in 
diminutive doses. 

Ques. 797. — Can superheated steam be used to advan- 
tage in steam-turbines? 

Ans. — It can; in fact the steam-turbine has solved the 
problem of superheated steam, owing to the absence of 
all rubbing parts exposed .to the steam. This permits the 
use of steam of high temperature thus making it possible 
to realize the advantages of economical operation. 

Ques. 798. — Is there not danger of distortion of the 
turbine cylinder being caused by the very high tempera- 
tures to which it is exposed by the use of superheated 
steam? 

Ans. — There have been numerous instances in the past 
of unequal expansion of the top, and bottom of the cylin- 
der thereby causing the rotating blades to come in 
contact with the cylinder walls, and be ripped out, but this 
difficulty has in a great measure been overcome by certain 
designers of steam-turbines, who have made a special 
study of the laws of expansion and contraction of metals^ 



354 QUESTIONS AND ANSWERS 

and have thus been enabled to make such a distribution 
of the metal, as to cause an equal expansion of all parts 
of the cylinder. 

Ques. 799. — What effect does the accidental carrying 
over of water with the steam, have upon the steam-tur- 
bine? 

Ans. — The sudden presence of a quantity of water 
with the steam, caused by foaming or priming of the boil- 
ers, would cause no more serious results than the slowing 
down of the turbine during the time necessary to permit 
the water to be discharged from the exhaust end. 

Ques. 800. — What may be said in general of the 
steam-turbine? 

Ans. — It has passed through the experimental stage, 
and has come to the front, as an efficient power pro- 
ducer, having a bright future before it. 



DE LAVAL STEAM TURBINE. 

CLASS C. 

Ques. 801. — In what respect does the Class C De 
Laval Turbine differ mainly from the regulation type of 
De Laval Turbine referred to on pages 304 to 314? 

Ans. — In the construction of the buckets, and guide 
vanes; also in the accessibility of the parts. 

Ques. 802. — Describe the construction of the buckets 
in this type of steam Turbine. 

Ans. — The buckets are made of nickel-bronze and 
are secured to the rim of the wheel by bulb shanks. 
They may also be replaced individually without disturb- 
ing other buckets. 



STEAM TURBINE FUNDAMENTAL PRINCIPLES 355 

Ques. 803. — Describe the construction of the guide 
vanes in the Class C Turbine . 

Ans. — The guide vanes are of nickel-bronze, and are 
attached to steel retaining rings in the same manner as 
are the rotating buckets. 

Ques. 804. — What can be said in favor of this meth- 
od of attaching guide vanes, and buckets? 

Ans. — It is superior to the common method of cast- 
ing these important parts of the turbine in with a por- 
tion of the casing, or the rim of the wheel. 
Ques. 805. — Give a reason for this. 
Ans. — If guide vanes, or buckets that are cast in, 
should become corroded, and need replacing, it is neces- 
sary to replace a portion of the casing, or the wheel rim, 
in order to bring the turbine back to its original effi- 
ciency. 

Ques. 806. — What amount of work is necessary in 
order to replace one, or more of these parts in the Class 
C De Laval Steam Turbine? 

Ans. — See answer to question 802. 

Ques. 807. — How are changes in boiler pressure, or 
in vacuum, provided for in the Class C Turbine ? 

Ans. — By simply replacing the nozzles by others de- 
signed for the new ratio of expansion. 

Ques. 808. — Is this possible in turbines in which the 
nozzles are a permanent part of the main turbine struc- 
ture? 

Ans. — It is not. 

Ques. 809. — How is the speed of the Class C De 
Laval Turbine controlled? 



S56 QUESTIONS AND ANSWERS 

Ans. — Two governors are provided, one of which is 
called the emergency governor. 

Ques. 810. — In what way may a turbine governor be 
rendered useless, and still retain all its parts unbroken ? 

Ans. — By the valves becoming clogged with scale, 
waste or other foreign matter. 

Ques. 811. — What special provision does this type of 
steam turbine possess for the prevention of accidents in 
case the emergency governor should fail? 

Ans. — The wheel itself is designed to withstand the 
highest speed, and in addition to this precaution, the en- 
tire wheel is encircled by a steel ring which would ef- 
fectually prevent the penetration of detached parts. 

Ques. 812. — How may the rotating parts of the 
De Laval Class C Turbine be removed entirely from the 
casing when repairs are necessary ? 

Ans. — By lifting the casing cover, and loosening and 
removing the bearing caps of the shaft. 

Ques. 813. — Why is it possible to maintain indefinite- 
ly a high steam economy with this type of steam tur- 
bine? 

Ans. — This is due to the fact that provision is made 
for the easy and quick replacement of those parts sub- 
ject to wear. 

Ques. 814. — Is the Type C De Laval Steam Turbine 
built in the larger sizes ? 

Ans. — It is not, at present. 

Ques. 815. — Mention some of the principal uses for 
which this turbine is adapted. 

Ans. — It is especially adapted to the driving of cen- 



STEAM TURBINE FUNDAMENTAL PRINCIPLES 357 

trifugal pumps, blowers, exciters, and small dynamos. 

Ques. 816. — Describe the various conditions of op- 
eration for which the Class C Steam Turbine is built. 

Ans. — It may be operated high pressure condensing, 
or high pressure non-condensing. It may also be op- 
erated with a certain degree of back pressure. Again, 
it may be operated as a low pressure condensing turbine, 
or it may be operated on mixed flow service. 



EXTRACTS FROM UNITED STATES GOVERN- 
MENT RULES FOR THE EXAMINATION 
OF APPLICANTS FOR ENGINEERS^ 
LICENSE. 

Ques. 817. — Give some of the principal regulations 
relative to Marine Engineers. 

Ans. — Before an original license is issued to any per- 
son to act as engineer, he must personally appear be- 
fore some local board, or a supervising inspector for 
examination; but upon the renewal of such license, 
when the distance from any local board, or supervising 
inspector is such as to put the person holding the same 
to great inconvenience, and expense to appear in person, 
he may upon taking the oath of office before any per- 
son authorized to administer oaths, and forwarding the 
same, together with the license to be renewed, to the 
local board, or supervising inspector of the district in 
which he resides, or is employed, have the same renewed 
by the said inspectors, if no valid reason to the contrary 
be known to them, and they shall attach such oath to 
the stub end of the license, which is to be retained on 



358 QUESTIONS AND ANSWERS 

file in their office. And inspectors are directed, when 
licenses are completed, to draw a broad pen and ink red 
mark through unused spaces in the body thereof, so as 
to prevent as far as possible, illegal interpolation after 
issue. 

Ques. 818. — Give in brief the classification of engi- 
neers on the lakes, and seaboard. 

Ans. — The classification of engineers on the lakes, 
and seaboard shall be as follows : 

Chief Engineer. 

First Assistant Engineer. 

Second Assistant Engineer. 

Third Assistant Engineer. 

Ques. 819. — AMiat limitations are placed upon chief 
engineers, and assistant engineers relative to their 
sphere of action? 

Ans. — Inspectors may designate upon the certificate 
of any chief, or assistant engineer the tonnage of the 
vessel on w^hich he may act.*' 

Ques. 820. — \A^hat additional restrictions are placed 
upon assistant engineers? 

Ans. — First, second, and third assistant engineers 
may act as such on any steamer of the grade of which 
they hold a license, or as such assistant engineer on any 
steamer of a lower grade than those to which they hold 
a license. 

Ques. 821. — On what grades of steamers may assist- 
ant engineers act as chief engineers ? 

Ans. — Assistant engineers may act as chief engi- 
neers on high pressure steamers of one hundred tons bur- 



STEAM TURBINE FUNDAMENTAL PRINCIPLES 359 

den and under, of the class and tonnage, or particular 
steamer for which the inspectors, after a thorough ex- 
amination, may find them qualified. In all cases where 
an assistant engineer is permitted to act as first (chief) 
engineer, the inspector shall state on the face of his cer- 
tificate of license, the class and tonnage of steamers, or 
the particular steamer on which he may so act. 

Ques. 822. — What is the duty of an engineer when 
he assumes charge of the boilers and machinery of a 
steamer ? 

Ans. — His duty is to forthwith thoroughly examine 
the same, and if he finds any part thereof in bad con- 
dition, caused by neglect or inattention on the part of 
his predecessor, he shall immediately report the facts to 
the local inspectors of the district, who shall thereupon 
investigate the matter, and if the former engineer has 
been culpably derelict of duty, they shall suspend or re- 
voke his license. 

Ques. 823. — What are some of the important require- 
ments regarding service that will entitle a person to re- 
ceive an original license as engineer or assistant engi- 
neer? 

Ans. — He must have served at least three years in 
the engineers' department of a steam vessel ; provided 
that any person who has served as a regular machinist 
in a marine engine works for a period of not less than 
three years ; and any person who has served for a period 
of not less than three years as a locomotive engineer, 
stationary engineer, regular machinist in a locomotive, 
or stationary engine works, and any person who has 



360 , QUESTIONS AND ANSWERS 

graduated as a mechanical engineer from a duly recog- 
nized school of technolog}'^, may be licensed as engineer 
on steam vessels, after having had not less than one 
year's experience in the engine department of a steam 
vessel. 

Ques. 824. — What are the requirements regarding 
education ? 

Ans. — No original license shall be granted any engi- 
neer, or assistant engineer, who cannot read and write, 
and does not understand the plain rules of arithmetic. 

Ques. 825. — What are the requirements regarding 
the age of an applicant? 

Ans. — He must be not less than twenty-one, nor more 
than thirty years of age in order to receive an appoint- 
ment as second assistant engineer. 

Ques. 826. — What is the penalty for making a false 
statement before a board of examination, or of produc- 
ing a false certificate as to age, time of service or char- 
acter ? 

Ans.— Any person found guilty of such action will 
be dropped immediately. 



INDEX 



A 

PAGE 

Absolute pressure 286 

Absolute zero 288 

Adiabatic curve 290-303 

Admission — 

Instant of 188 

Air- 
Admission to furnace 8-5 

Advantage in heating 131 

Composition of 17 

Locks, object of 124-126 

Product of 18 

Volume required for combustion 17-19 

Air pump — 

Description of 225-226 

Dimensions of 218 

Types of 224-225 

Valves for 227 

Angular advance 191 

Apparatus — 

Condensing, for steam turbines 338 

Ash— 

Dry 144 

Ash ejector 127 

Ash pits — 

Closed 123 

B 

Blov^-off — 

Surface .. 112 

Bottom 113 

Boilers — 

Bracing 66 

Back arch for horizontal tubular 82-83 



INDEX 

PAGE 

Connecting up 138-139 

Feed pump 97 

Heating surface 86-87 

Horsepower 86-87 

Leaks 135 

Marine 169 

Material 65 

Operation 128 

Rivets 66 

Seams, welded 76 

Steam space of 110 

T3^pes of 25-64 

Washing out 134-136 

Boiler construction 65 

Boyles law 14, 290 

Braces 66 

Bucket speed 304 

Bursting pressure , 77 

C 

Calorimeter 14^ 

Carbon 17 

Carbon, monoxide 21 

Clearance 302 

Piston 289 

Steam , 289 

Coal — 

Composition of 22 

Consumption of 156 

Dry 145 

Heating value of one pound 24 

Method of ascertaining cost 154-155 

Moisture in 145 

Cocks — 

Asbestos packed 117 

Gauge 104 

Hydrometer o 114 

Combustible — 

Weight of 145 

Combustion 17 



INDEX 

PAGE 

Rate ot 20 

Compression 302 

Advantage of 189 

Instant of 188 

Meaning of 289 

Condensation 233-235 

C3dinder^ 293 

Condenser — 

Advantages in use of 214-215 

For steam turbines 338 

Jet 217 

Siphon 216 

Surface 213 

Corrosion 168 

Cause of 169 

Prevention of 170 

Curves — 

Adiabatic 290-303 

Expansion 290 

Isothermal , o 290 

Cut-off- 
Adjustable 295 

Fixed 295 

Instant of 188 

D 

Dampers — 

Funnel 117-118 

Dead-center 202-208 

Diagram — 

Characteristics of 296 

Details of 235-286 

Method of taking 284-285 

Distillers 253-254 ' 

Draught 19 

Artificial 19-122 

Essentials for 150 

Forced 122-124 

Measuring 150-151 

Natural 19, 122 



INDEX 

PAGE 

Systems 131-132 

Draught gauge 150 

Dry-pipe 112 

Dynamics 291 

D3'namos — 

For marine service 260-264 

E 

Eccentric — 

Description of 190 

Position 191-204 

Throw of , 191 

Efficiency — 

Plant 292 

Steam 291 

Ejector — 

Ash , 127 

Engine — 

Automatic 294 

Classes of 173-178 

Four-valve » 185 

Marine 192 

Variable cut-off 294 

Evaporation — 

Equivalent 152 

Factor of 153-154 

Of water 152 

Evaporation tests — 

Apparatus for 141 

Data for 148 

Duration of 148 

Method of conducting 141 

Objects of 140 

Preparing for 146-147 

Evaporators — 

For marine " service 253-254 

Exhaust steam — 

Disposal of 337 

Expansion 13 

Advantages of 179 



INDEX 

PAGE 

Curve , . . . , 290 

Joint 116 

Rate of 181 

Ratio of 288 

F 
Feed pumps 97 

Feed water — 

Average temperature of 145-146 

Heaters 247-248 

How supplied to boiler 139 

Stoppage of supply 140 

Fire cleaning 129 

Firing — 

Hand 130 

Fire-main 269 

Fire tools , 128 

Foot pound. , 290 

Force 291 

Forced draught 122-124 

Friction — 

In steam turbines 341 

Fuels 167 

Funnel-stays 119 

Funnel cover 121-122 

Furnace — 

Corrugated 26- 78 

Petroleum 165 

Temperature of 21 

Fusible plug 106-107 

G 

Galvanic action 170 

Cause of '. 170 

Prevention of 171 

Gases — 

Escaping 146 

Gauge — 

Cock 104 

Steam 107-1 10 



INDEX 

Governor — page 

Adjustment of 209-210 

Curtis steam turbin*^, ^ , . 321 

Dunlop's 250-253 

Inertia 204-205 

Isochronal 204-295 

Marine 250 

Object of 249 

Principle of 249 

Shaft 295 

Throttling 294 

Grate-bars — • 

Dimensions of 84 

Types of 85-86 

Grate-surface 84-85 

Grease filters 249 

H 

Hand firing 130 

Disadvantages of 156 

Heat- 
Latent 15 

Loss of 131 

Mechanical equivalent of 16 

Radiation of 16 

Sensible 15 

Specific 14 

Transmission of 16 

Horsepower — 

Boiler 155 

Constant 289 

Engine 289 

Indicated 289 

Net 289 

Hot-well 228-229 

Hydrometer 115 

Hydrometer cock 114 

I 

Indicator — 

Care of 282-283 

. Construction of 272-273 



INDEX 

PAGE 

Diagram 276-277 

Principles of 271 

Injector — 

Principles of 101 

Isothermal curve 290 

J 

Jet condenser . '. 217 

Jet speed » 304 

L 

Lap 187 

Inside 188 

Outside 188 

Latent heat 15 

Lead 188 

Decreasing , 203 

Equalizing 203 

Object of 189 

Lighting— 

In marine service 265-266 

Link — 

Block 195 

Curvature of o 194 

Slip of 195 

Link-motion 192 

Locks — 

Air 124-126 

M 
Mean effective pressure 287-297 

Method of finding. ,.. 299 

Mechanical stokers 157 

Types of 157-161 

Moisture — 

In coal 145-15^ 

In steam 145 

Momentum 291 

Motion— 

Frst law of 290 



INDEX 

o 

Oil — PAGE 

Composition of 24 

Fuel 24 

Heating value of 24 

Ordinates 293 

Oxidation 169 

P 

Petroleum — 

Advantages in use of 166-167 

Analysis of 164 

Heating value of 165 

Method of inducting to furnace 166 

Obj ection to 167 

Piston — 

Balancing 202 

Piston clearance 289 

Piston displacement 289 

Piston speed .- 289 

Plaximeter „ 300-301 

Plates- 
Oxidation of , , 169 

Power — 

Definition 290 

Pressure — 

Absolute 286 

Absolute back 287 

Back • 287 

Boiler 286 

Bursting 77 

Condenser 288 

Expansion of 13 

Gauge 286 

Initial 286 

Mean effective 287 

Safe working 77 

Terminal 286-287 

Pumps — 

Air 215 

Bilge 266-267 



INDEX 

PAGE 

Boiler feed 241 

Centrifugal 231 

Circulating 230 

Double acting , 242-246 

Dry air 839 

Duplex 97 

Fire, marine 267-268 

For marine service 240 

Location of 241 

Petroleum 166 

R 

Ratio— 

Of cylinder volumes » 179 

Receiver 179-180 

Reducing motion 280 

Reducing wheel 279 

Re-evaporation — 

Cylinder 293 

Refrigeration — 

Cold air .system 255-258 

Carbonic acid system 259-260 

Release — 

Instant of 188 

Rivets — 

Material for 66 

Test for 66 

Riveted joints — 

Efficiency of 72-74 

Lloyd's rules for 75 

Rocker arm — 

Adjustment of • 206 

Rules— 

For finding heating surface of various types of boilers. .87-89 

For finding heating surface of corrugated flues 90 

For finding area of lever safety valves 93 

For finding speed of pump 98 

For finding velocity of flow in discharge pipe 98-99 

For finding required size of feed pump 100-101 

For finding boiler horsepower , 156 



INDEX 

PACK 

For finding weight of condensing water 234-235 

Rules— 

For finding I. H. P 301 

For finding bursting pressure 77 

For finding safe working pressure 77 

S 

Safe working pressure 77 

Safety valve — 

Duty of 90 

Types of 91-92 

Scale 137 

Sea water 170 

Composition of 211 

Disadvantages in using 212 

Sensible heat 15 

Separator 1 16-118 

Siphon condenser 216 

Siren, steam 112-113 

Smoke and soot 21 

Specific heat 14 

Speed — 

Bucket 304 

Jet 304 

Piston 289 

Regulation in Curtis turbine 321 

Regulation in Hamilton-Holzworth turbine 335-336 

Steam 304 

Stays — 

Gusset 67 

Funnel 119 

Material for 67-68 

Stay bolts 71-72 

Steam 7 

Action of in engine cylinder 173 

Clearance 289 

Consumption per H. P. hour 292 

Dry 145 

Gauge 107 

Maximum theoretical duty of 291 

Moisture in 145 



INDEX 

PAGE 

Physical properties of 8-12 

Relative volume of 7 

Theorerical velocity of 305 

Volume of 7 

Wire drawn 288 

Steam efficiency 291 

Steam gauge 107-110 

Steam siren. 112-113 

Steam speed 304 

Steam turbine — 

Action of steam in 304 

Advantage over reciprocating engine 305-30ti, 322-340 

Allis-Chalmers 342 

Curtis (descriptive) 314-321 

De Laval (descriptive) 306-314 

Friction in 341 

Hamilton-Holzworth 330-337 

Principles of 304 

Westinghouse-Parsons 323-330 

Stoke-hold — 

Closed 126-127 

Stokers — 

For marine service 164 

Fuel for 164 

Mechanical 157 

Method of supplying coal to 163-164 

Underfeed 162-163 

Surface condenser — 

Advantages of 213 

Construction and action of 219 

' Tubes of..,. 221-222 

T 

Tables — 

Analysis of coal 23 

Areas and circumferences of circles 237-238 

Capacities and speed of De Laval turbines 314 

Diameters of rivets 73 

Factors of evaporation 155 

Lap and lead of Corliss valves 209 

Physical properties of saturated steam 8-12 



INDEX 

PAGE 

Proportion of triple riveted butt joints 76 

Specific heat of various substances 14-15 

Water required for jet condensers 235 

Weight of water at various temperatures 144 

Tests — 

Evaporation 140 

For efficiency of boiler 149-152 

Test piece 65-66 

Thermal unit 16| 

Thermo-dynamics 15 

Thermometer — 

Hot water 146 

Tubes — 

Cleaning 133-137 

Fire 25 

Galloway 37 

Material for 6Q 

Submerged 25 

Water 25 

Working test for 66 

Turbines — 

Action of steam in 304 

Advantage over reciprocating engine 305-306, 322-340 

Allis-Chalmers 342 

Curtis (descriptive) 306-314 

De Laval (descriptive) .314-321 

Friction in 341 

Hamilton-Holzworth 330-337 

Principles of 304 

Westinghouse-Parsons 323-330 

V 

Vacuum — 

How measured 213 

How maintained 215-219 

In turbine condensers 340 

Meaning of 213 

Perfect 287 

Vacuum gauge — ^ 

Mercurial 214 

.Spring 214 



INDEX 

Valves — PAGE 

Check 104 

Double-ported 199 

Piston 202 

Poppet 199 

Treble-ported 200 

Safety 90 

Setting 202-205 

Sea 239 

Slide 186-187 

Steam stop 110 

Steam stop, automatic Ill 

Valve gear — 

Joy 196 

Marshall 195 

Reversing 194-195 

Valve-setting 202-205 

Defects in 297 

W 

Water- 
Evaporation per pound of coal 152 

Sea 170^211 

Quantity required for condenser 233 

Water column 105-106 

Whistle- 
Steam 111-112 

Wire drawing 288-297 

Wood- 
Composition of 24 

Disadvantage of as fuel..- 24 

Heating value of, in thermal units 24 

Work- 
Definition of 291 

Unit of 290 

Wrist-plate — 

Vibration of 207 

z 

Zero- 
Absolute 288 

Zinc slabs 171-172 



MECHANICAL DRAWING 

AND 

MACHINE DESIGN 



DRAFTING TOOLS. 

Compasses. These, as well as all other instruments, 
should be chosen with great care on account of their 
variety in shape and quality. Drafting instruments are 
as a rule made of German silver and steel. The steel 
should be of the best grade and carefully tempered. 
The material used in the manufacture of some instruc 
ments is of so poor a quality that it neither holds its 
shape nor wears well. It is better therefore when buy- 
ing, to select instruments of high grade, and which 
are made of the best German silver and a good quality 
of steel, as the joints are always carefully fitted and 




Fig. 1 — Compass Set. 



they will withstand the constant usage of many years. 
A compass set of convenient form is shown in Pig. 1. 
It has three removable parts : the pencil-point, the pen- 
point, and the lengthening-bar. There is a hinged joint 
in each leg of the compass and the socket for the re- 
movable legs is provided with a clamping screw. The 
shanks of the removable legs should be a nice fit in 
the socket and require scarcely any effort to remove. 



2 MECHANICAL DRAWING 

They should, however, stay in the socket without being 
held by the clamping screw. The lengthening bar is 
used to extend the pen or pencil-legs when drawing 
large circles. 




Fig. 2 — Pen and Pencil Compasses. 



A pen and pencil compass set of smaller size, without 
detachable legs are shown in Fig. 2, these instruments 
will be found useful in many cases as a medium be- 
tween the large compasses and the spring-bow set. 





Fig. 3 — Compass Joints. 

The most important part of a pair of compasses is 
the head, which forms the hinged joint. There are two 
forms of joints: the tongue- joint, as shown in the left- 
hand view in Fig. 3, in which the head of one shank has 
a tongue, generally made of steel, which moves be- 
tween two lugs on the other shank, and the pivot joint, 
as shown in the right-hand view in Fig. 3, in which 
each shank is reduced to half its thickness at the head. 
These shanks are surrounded by a clamp or yoke, 



DRAFTING TOOLS 3 

which carries two cone-pointed set-screws, one in each 
side, the points of these screws working in counter- 
sinks in the yoke. The yoke is provided with a milled 
or knurled handle to manipulate the compass. The 
head joint of the compass should move freely and 
evenly throughout its entire movement, and not stiff 
at one point and loose at another. It should also be 
tight enough in the joint to hold its adjustment when 
once set. Figure 4 shows the method of holding a 
compass, and the correct position of the fingers before 
and after describing a circle. The non-removable leg 
of the compass should carry a needle-point, that may 




Fig. 4 — Correct Manner of Holding a Compass. 



be easily replaced if lost or damaged, and it should 
have a shoulder to prevent the point from sinking into 
the paper beyond a certain depth. The needle-point 
should also be capable of being adjusted in or out, and 
fastened securely at any desired point, thus making 
the leg of the compass a little longer or shorter as may 
be desired. 



4 MECHANICAL DRAWING 

The socket for the lead in the pencil-point should 
hold the lead firmly without the necessity of wedging 
it in the socket by means of paper or small pieces of 
wood. 

When first adjusting the compass for use, place the 
pen-point in the instrument and securely clamp it in 
place, firmly against the shoulder of the socket, then 
adjust the needle-point so that its point is even with 
that of the pen. When once properly adjusted the 
needle-point should not be changed. The needle-point 
is usually made with a cone-point at one end and a 
fine shouldered-point at the other. The cone-point 
should never be used, as it makes too large a hole in 
the drawing paper. 




Fig. 5 — Hair Spring Dividers. 



Hair Spring* Dividers. Dividers such as are shown 
in Fig. 5 are used for laying off equal distances and for 
transferring measurements from one part of a draw- 
ing to another, or from one drawing to another. They 
consist of steel points set in German silver shanks 
which are hinged together. The joints of the dividers 
should work smoothly, the legs come close together, 
and the steel points should be sharp and of the same 
length. One of the legs of the dividers has a spring 
controlled by an adjustable thumb-nut. By means of 
this device, from which the instrument gets its name, 
the adjustable leg may be moved a trifle after the 
rough or approximate adjustment of the dividers has 
been made. 



DEAFTING TOOLS 5 

Spring-bow Instruments. The spring-bow dividers, 
pencil and pen, as shown in Fig. 6, are for the purpose 
of describing small circles and laying off distances of 
very small dimensions and are very convenient for 
these purposes. Any form of spring-bow instruments 
with interchangeable or removable legs will be found 
very unsatisfactory. The legs should be made of one 
piece of steel, to which the handle is attached. Any 




Fig. 6 — Spring-bow Instruments. 

instrument in which the legs are separate pieces fast- 
ened to the shank are undesirable, because the parts 
are liable to become loose. The spring-bow dividers are 
used like the hair-spring dividers, for the spacing of 
distances, they have the advantage of being fixed in 
any position so that there is no liability of a change of 
measurement by the handling of the instrument. When 
spacing distances the divider is rotated alternately 
right and left, with the forefinger on top of the handle. 



6 MECHANICAL DRAWING 

Ruling Pens. Ruling pens are of two different kinds, 
one kind with a hinge joint to allow the blades to be 
opened for cleaning and the other kind without a joint 
and made from a solid piece of steel. Two sizes of 
ruling pens with hinged joints are shown in Fig. 7. 
The joint in this style of pen should be very carefully 




Fig. 7 — Ruling Pens with Hinged Blade. 

made, otherwise the hinged blade will very soon be- 
come loose and render the pen useless. The best kind 
of pen for general use is the kind shown in Fig. 8, in 
which the upper blade springs open when the adjust- 
ing screw is removed from the lower blade. A pen 




Fig. 8 — Ruling Pen with Spring Blade. 



such as the one just described is to be preferred to one 
with a joint, no matter how well made it may be. 
Ruling pens with broad nibs and flat handles, as shown 
in Fig. 9, are preferred by many draftsmen, they hold 
a large quantity of ink and make a very uniform line. 



DRAFTING TOOLS 7 

The position in which a ruling pen should be held 
when drawing lines perpendicular to the T-square is 
shown in Fig. 10. The drawing board should be placed 




Fig. 9 — Ruling Pens with Wide Blades. 

so as to permit the light to come from the upper left- 
hand corner, this position of the T-square and triangle 




Fig. 10 — Correct Manner of Holding a Ruling Pen. 

will avoid any possibility of the shadows of the T- 
square blade or triangle being cast on the lines to be 
drawn. 



8 MECHANICAL DRAWING 

Sharpening a Ruling Pen. The blades of the pen 
should be curved at the points, and elliptical in shape. 
To sharpen the pen, screw the blades together and 
then move the pen back and forth upon a fine oil-stone, 
holding it in the position it should have when in use, 
but moving it so that the points are ground to the same 
length, and to an elliptical form. AVhen this form has 
been secured, draw a folded piece of the finest emery 
paper two or three times between the blades, which are 




Fig. 11 — Complete Set of Instruments in Case. 



pressed together by the screw. This will remove any 
roughness from the inner surfaces of the blades, these 
surfaces should not be ground upon the oil-stone. 

AVhen the blades are ground to the proper shape, 
they must be placed flat upon the stone and ground as 
thin as possible without giving them a cutting edge. To 
do this, the pen should be moved back and forth and 
slightly revolved at the same time. Both blades must 
be made of equal thickness. If either blade is ground 
too thin, it will cut the paper as would a knife, and 



DRAFTING TOOLS 9 

the process must be repeated from the beginning. In 
order to see the condition of the blades, they should 
be slightly separated while being brought to the proper 
thickness. 

Drafting Instruments. A leather-covered case with 
a complete set of instruments in a velvet lined tray is 
shown in Fig. 11. This outfit is sufficient to fulfill the 
requirements of any ordinary draftsman in the way of 
instruments. 

T-Square. The length of a T-square is always meas- 
ured by the length of the blade outside of the head. 
The T-square should always be as long as the draw- 
ing board, and if possible a little longer. For the gen- 
eral run of work the head of the T-square should be of 
a single and fixed piece, that is fastened permanently 
to the blade. The head should have its upper inside 



I 



Iff 



.,s 



Fig. 12 — Slanting Blade T-SquaTe. 

corner rabbeted, so that the guiding edge of the head 
may be trued up when occasion demands it. A very 
convenient form of T-square is shown in Fig. 12, which 
has a slanting blade, the working edge of which is 
lined w^ith ebony. 

More elaborate forms of T-squares are sometimes 
used, in which the head is double and one side swivels 



10 



MECHANICAL DRAWING 



in order to draw parallel lines other than horizontal. 
The adjustable or swivel head is clamped in any de- 
sired position by means of a thumb-screw. 



Fig. 13 — 60 and 45 Degree Triangles. 

Triangles or Set-Squares. Triangles are made of 
wood, hard rubber or transparent celluloid. The prin- 
cipal forms of triangles are shown in Figs. 13 and 14, 




Fig. 14 — 15 Degree Triangle. 

which are 60°, 45° and 15° respectively. The two 
triangles generally used by draftsmen are the 60° and 
45°. The former has angles of 30°, 60° and 90°. The 
latter two 45° and a 90° angle. 



DRAFTING TOOLS 11 

Testing Triangles. Place the triangle on the T- 
square with the vertical edge at the right, draw a fine 
line in contact with this edge, then reverse the triangle 
and move the vertical edge towards the line. If the 
vertical edge of the triangle and the line coincide the 



7 je /////// / yf 

Fig. 15— Flat Beveled-edge Scale. 

angle is 90°. If they do not coincide, and the vertex 
of the angle formed by the line and the vertical edge 
of the triangle is at the top, the angle is greater than 
90° by half the angle indicated. If the vertex of the 
angle is below, the angle is less than 90° by half the 
amount indicated. 

n \ \ \\\ \ i I u\ w \ w \ \\ \\ \ n\ \ VI 

Fig. 16 — Triangular Scale. 

Scales. The best and most convenient form of scale 
for general use is that shown in Pig. 15. Another form 
of scale which is very commonly used is shown in Fig. 
16. The ordinary length of a scale is 12 inches, not 
counting the small portion at each end, which is undi- 
vided, and whose use is to protect the end graduations 
from injury. A scale should be used for dimensioning 



12 



MECHANICAL DRAWING 



drawings only, and not used as a ruler or straight- 
edge. The measurements should be taken directly 
from the scale by laying it on the drawing, and not by 
transferring the distances from the scale to the draw- 
ing by means of a pair of dividers. 




Fig. 



Ourves. For inking in lines which are neither 
straight lines nor arcs of circles, it is necessary to use 
curves. They are made in a great variety of forms as 
illustrated in Fig. 17, but the form similar to that illus- 



DRAFTING TOOLS 



13 



trated in Fig. 18 will be found the most useful. They 
are made of wood, hard rubber and celluloid. Many 
curved lines can be inked in by means of a compass, 
but when the radius is too great, a curve should be 
used. 

Paper. The paper must be tough and should have a 
surface which is not easily roughened by erasing lines 
drawn upon it. This is important when drawings are 
to be inked. For all mechanical work, the paper should 
be hard and strong. 




Fig. 18 — Useful Form of Curve. 



For pencil drawings a paper which is not smoothly 
calendered is best, because the pencil marks more read- 
ily upon an unpolished paper, and because its surface 
will not show erasures as quickly as that of a smooth 
paper. For sketching, several kinds of paper, which 
are good enough for the work, may be obtained both 
in sheets, in block form, and also made up in blank 
books. 



14 MECHANICAL DRAWING 

Whatman's paper is the best for drawings which 
are to be inked. There are two grades, hot and cold 
pressed, suitable for this use, the cold-pressed having 
the rougher surface. If the paper is not to be stretched, 
the cold-pressed is preferable, as its surface shows 
erasures less than that of the hot-pressed. The side 
from which the water-marked name is read is the right 
side, but there is little difference between the two sides 
of hot and cold pressed papers. Stretching the paper 
is unnecessary except when colors are to be applied by 
the brushy or when the most perfect inked drawing is 
desired. 



Fig. 19 — Correct Manner of Sharpening a Pencil. 

Pencils. Lead pencils for drafting use are made of 
different degrees of hardness and each kind of pencil 
has its grade indicated by letters stamped on it at one 
end. The grade of pencil mostly used by draftsmen 
is 4 H, a 6 H, pencil is too hard and unless used with 
great care will indent the paper so that the pencil 
marks cannot be erased. A 4 H pencil requires greater 
care and more frequent sharpening, but the draftsman 
will in this manner acquire a lighter touch, which is 
of much value. Drafting pencils should always be 
sharpened to a chisel or wedge-shaped point, as shown 
in Fig. 19, the finishing of the point should always be 



DRAFTING TOOLS 15 

completed with a fine file or a sand paper pencil sharp- 
ener, but never with a knife. In drawing the pencil 
should be held vertical, or nearly so, the arm free from 
the body, and the flat side of the chisel-point lightly 
touching the edge of the blade of the T-square. Al- 
ways draw from left to right, or from the bottom to the 
top of the board. 

Pencil Sharpeners. Pencil sharpeners or pointers 
are of many different kinds, from a piece of fine sand 
paper or a file to quite complicated machines. For 
ordinary use a sand paper block from which the sheets 




Fig. 20 — Sandpaper Pencil Sharpener. 



can be removed as soon as worn out, will be found the 
;most convenient, as shown in Fig. 20. In sharpening 
a drafting pencil remove the wood from the end by 
means of a sharp knife, exposing about one-fourth to 
three-eighths of an inch of the lead. The end of the 
lead should then be sharpened to a chisel or wedge- 
shaped point on the sand paper block. 

Pencil Erasers. A pencil eraser or rubber should 
be of soft, fine-grained rubber, free from sand or grit 
and having no tendency to glaze or smear the surface 
of the drawing paper. A pencil eraser of the kind 
shown in Fig. 21 will be found very satisfactory for 
general use. 



16 



MECHANICAL DRAWING 



Ink Erasers. Inked lines should always be removed 
from the drawing by means of a sand-rubber, which is 
known as an ink eraser, but never by scratching the 
surface of the paper with a knife. As all drawing 
inks dry rapidly, and should not penetrate the surface 
of the paper, the object in erasing is to remove the ink 
from the surface of the paper without injury to it. 
An ink eraser, such as shown in Fig. 22, will leave the 
surface of the drawing in good condition to again re- 
ceive ink. 




Fig. 



-Pencil Rubber or Eraser. 



Fig. 22 — Ink Rubber or Eraser, 



Eraser Guard. An eraser guard or shield, which is 
used to protect other lines when removing an inked 
line from the surface of the drawing paper, consists of 
a thin sheet of flexible metal, usually brass, provided 
with slots and holes of various shapes and sizes. The 
shield or guard permits erasures to be made of limited 
size without damage to the rest of the drawing. 

Drawing" Ink. Black drawing ink, preferably, some 
make of waterproof ink, is to be had in liquid form, as 
shown in Fig. 24. The liquid ink is preferable to the 
Indian or Chinese stick inks, as shown in Fig. 25, 
which take considerable time to prepare, besides neces- 
sitating fresh mixing each time the ink is used. 



DEAFTING TOOLS 



17 




Fig. 23 — Erasing Guard or Shield. 





i >•?. 24 — Waterproof Black Drawing Ink. 




Fig. 25 — Chinese Stick Black Drawing Ink. 



18 



^lECILlXICAL DRAWING 



Protractor. A protractor is a circnlar scale and is 
divided into degrees and fractions of a degree. Pro- 
tractors are made both circular and semi-circular in 
shape^ the latter being the ordinary and most com^ 
monly nsed form, as sho^vn in Fig. 26. Protractors 
are made of paper, horn, brass. German silver and 
steel. Protractors usually have their edges bevelled 
so as to bring the divisions on the scale close to the 
drawing paper. A semi-circular protractor is to be 




Fig. 26^German Silver Protractor. 



preferred for all ordinary work. A semi-circular pro- 
tractor has a straight edge upon which the center of 
the circle is marked, so that the protractor may be 
readily applied to the point at which it is desired to 
read or lay off an angle. 

Drawing" Boards. A drawing board for ordinary 
use should be about 20 by 27 inches in size. The 
material should be of first quality clear soft pine, free 
from pitch and thoroughly kiln dried. The board 
should be made of five or six strips about 4 by 27 
inches, well glued together and held from warping by 
-^wo cleats on the back, as shown in Fig. 27. 



DRAFTING TOOLS 19 

The working edge of the drawing board should be 
tested from time to time, as any unevenness in this 
edge will impair the accuracy of the drawing. Some 
draftsmen use the lower edge of the board when draw- 
ing long lines parallel to the working edge. This neces- 
sitates making this edge true, and the angle between 
this and the working edge exactly 90° 




Fig. 27 — Drawing Board with Cleats on Back. 

Thumb-Tacks. Thumb-tacks are made of German 
silver or brass disks with pointed steel pins in their 
centers. The heads or disks should have very thin 
edges in order that the T-square may readily slide 
over them. 

Lettering Triangle. A triangle or set-square for lay- 
ing out lettering is shown in Fig. 28. The use of this 
triangle is plainly indicated by its name. 

Section Liners. A section liner is a device for draw- 
ing a series of parallel lines equi-distant from each 
other. One form of section liner is shown in Fig. 29. 
Its operation is as follows : Place the instrument in the 
position shown in the drawing, and rule a line along 
its vertical edge. Hold the straight-edge firmly in 



20 



MECHANICAL DRAWING 



place, and slide the triangle along it until the other 
side of the tapered edge of the tongue comes in contact 
with the other stud and holds it in this position, then 
allow the straight-edge to be drawn forward by the 
spring. Then draw a second line which will evidently 
be parallel to the first. The distance between the lines 
is regulated by moving the tongue in or out between 
the studs, as far as desired. 



I 




Fig. 28 — Lettering Triangle. 



Fig. 29 — Section Liner with 
Vertical Adjustment. 



Another form of section liner is shown in Fig. 30, 
having a horizontal instead of a vertical adjustment to 
regulate the width of the spacing. 

Beam Ctompasses. A beam compass is not, as a rule, 
included in a draftsman's outfit, but every well 
equipped drafting room should have one. A beam com- 



DRAFTING TOOLS 21 

pass is shown in Fig. 31, with removable legs and pen, 
pencil and needle-points. The right-hand leg in the 




Fig. 30 — Section Liner with Horizontal Adjustment. 



Fig. 31 — Beam Compass with Pen, Pencil and Needle- Points. 

illustration has a horizontal adjustment of about one- 
half an inch, operated by the milled thumb-nut shown. 



22 MECHANICAL DRAWING 

Water Colors. These may be obtained in the form 
of a thick paste in small porcelain pans, or in thin 
paste or semi-liquid form in collapsible tubes. The 
colors in tubes are liable to get hard, in which case 
they cannot be expelled from the tubes by pressure. 
The caps to the tubes also get stuck in place by the 
colors and are often removed with much difficulty. For 
the draftsman's purposes the moist colors in pans will 
be found the most satisfactory. 




Moist Water Colors in Case. 



.^ box of moist water colors is illustrated in Fig. 
32. The colors should be kept in a box of this kind, 
which can also be used as a palette. The box keeps all 
dust and dirt from the colors and prevents them from 
drying out rapidly. 



DRAFTING TOOLS 



23 



Water Color Brushes. These are made from black 
or red sable and camel's hair. Black sable brushes 
are too expensive for the draftsman's ordinary use. 

The best grade of camel's hair brushes such as are 
shown in Fig. 33, will be found quite satisfactory for 
ordinary use. 




Fig. 33 — Water Color Brushes. 



To ascertain whether a brush is of good quality or 
not, dip it in water until thoroughly wet, and then 
remove the water from it by a quick motion. The 
brush if of good quality should assume a convex shape, 
come to a fine point and also preserve its elasticity. 



GEOMETEICAL DEFINITIONS OP PLANE 
FIGURES. 

A line is the boundary or limit of a surface. 

A line has only one dimension, that of length. 

A point is considered as the extremity or limit of a 
line. The place where two lines intersect is also a 
point. A point has position but no dimensions. 

In practical work a point is represented by a fine 
dot. 

Lines may be either straight, broken or curved. 

A straight line is one which has the same direction 
throughout its length. 

A straight line is also called a right line. 

A straight line is usually called a line si^nply, and 
when the word line occurs it is to be understood as 
meaning straight line unless otherwise specified. A 
straight line is the shortest distance between two 
points. If any other path between the points were 
chosen, the line would become curved or broken. 
Therefore two points determine the position of the 
straight line joining them. 

A broken line is one which changes direction at one 
or more points. 

A curved line is one which changes direction con- 
stantly throughout its length. The word curve is used 
to denote a curved line. 

Lines may be represented as full, dotted, dashed, or 
dot-and-dashed. 

24 



GEOMETRICAL DEFINITIONS 25 

A full line is one which is continuous throughout its 
length. 

A dotted line is one which is composed of alternate 
dots and spaces. 

A dash line is one which is composed of alternate 
dashes and spaces. 

A dot-and-dash line is one which is composed of dots, 
spaces and dashes. These may be arranged in several 
ways according to the character of the line, that is, the 
meaning it is to convey. 

Surfaces may be either plane or curved. A plane 
si^rface is usually called a plane. 

A plane is such a surface that if a straight line be 
applied to it in any direction, the line and the surface 
will touch each other throughout their length. 

A curved surface is one no part of which is a plane. 

Any combination of points, lines, surfaces or solids 
is termed a figure. 

A plane figure is one which has all of its points in 
the same plane. 

Plane geometry treats of figures whose points all 
lie in the same plane. 

Lines may be so situated as to be parallel or inclined 
to each other. 

Parallel lines are those which have the same or 
opposite directions. Parallel lines are everywhere 
equally distant. Parallel lines will not meet however 
far produced. 

Inclined lines are those other than parallel. Inclined 
lines will always meet if produced far enough. Their 
mutual inclination forms an angle. 

The extremities of a surface are lines. 



26 MECHANICAL DRAWING 

A plane rectilineal angle is the inclination of two 
straight lines to one another in a plane which meet to- 
gether, but are not in the same straight line as in 
Fig. 34. 



Fig. 34. Fig. 35. 

When a straight line, standing on another straight 
line, makes the adjacent angles equal to one another, 
each of the angles is called a right angle and the 
straight line which stands on the other is called a per- 
pendicular to it as in Fig 35. 



Fig. 36. 

An obtuse angle is that which is greater than a right 
angle as in Fig. 36. 

An acute angle is that which is less than a right 
angle as in Fig. 34. 

A term or boundary is the extremity of anything. 



GEOMETRICAL DEFINITIONS 



27 



An equilateral triangle is that which has three equal 
sides as in Fig. 37. 

An isosceles triangle is that which has two sides 
equal as in Fig. 38. 





Fig. 37. 



Fig. 38. 



A scalene triangle is that which has three unequal 
sides as in Fig. 39. 

A right angled triangle is that which has a right 
angle as in Fig. 40. 




Fig. 39. 



Fig. 40. 



An obtuse-angled triangle is that which has an ob- 
tuse angle as in Fig. 39. 

The hypothenuse in a right-angled triangle is the 
side opposite the right angle as in Fig. 40. 



28 



MECHANICAL DRAWING 



A square is that which has all its sides equai and all 
its angles right-angled as in Fig. 41. 

A rectangle is that which has all its angles right 
angles, but only its opposite sides equal as in Fig. 42. 




Fig. 41. 



Fig. 42. 



A rhombus is that which has all its sides equal, but 
its angles are not right angles as in Fig. 43. 

A quadrilateral figure which has its opposite sides 
parallel is called a parallelogram as in Figs. 41, 42 
and 43. 

'A line joining two opposite angles of a quadrilateral 
is called a diagonal. 




Fig. 43. 



Fig. 44. 



An ellipse is a plane figure bounded by one continu- 
ous curve described about two points, so that the sum 
of the distances from every point in the curve to the 
two foci may be always the same — Fig. 44. 



PROPERTIES OF THE CIRCLE. 

A circle contains a greater area than any other plane 
figure bounded by the same length of circumference or 
outline. 

A circle is a plane figure contained by one line and is 
such that all straight lines drawn from a point within 
the figure to the circumference are equal, and this 
point is called the center of the circle. 

A diameter of a circle is a straight line drawn 
through the center and terminated both ways by the 
circumference, as AC in Pig. 45. 




Fig. 45. 

A radius is a straight line drawn from the center to 
the circumference, as LH in Fig. 45. 

A semicircle is the figure contained by a diameter 
and that part of the circumference cut off by a diameter 
as AHC in Fig. 45. 

29 



30 



MECHANICAL DRAWING 



A segment of a circle is the figure contained b^ a 
straight line and the circumference which it cuts off, 
as DHE in Fig. 45. 

A sector of a circle is the figure contained by two 
straight lines drawn from the center and the circumfer- 
ence between them, as LMC in Fig. 45. 

A chard is a straight line, shorter than the diameter, 
lying within the circle, and terminated at both ends 
by the circumference as DE in Fig. 45. 

An arc of a circle is any part of the circumference as 
DHE in Fig. 45. 

The versed sine is a perpendicular joining the mid- 
dle of the chord and circumference, as GH in Fig. 45. 




Fig. 46. 



Circumference. Multiply the diameter by 3.1416, the 
product is the circumference. 

Diameter. Multiply the circumference by .31831, 
the product is the diameter, or multiply the square 
root of the area by 1.12837, the product is the diameter. 

Area. Multiply the square of the diameter by .7854, 
the product is the area. 

Side of the square. Multiply the diameter by .8862, 
the product is the side of a square of equal area. 



GEOMETRICAL DEFINITIONS 



31 



Diameter of circle. Multiply the side of a square by 
1.128, the product is the diameter of a circle of equal 
area. 

To find the versed sine, chord of an arc or the radius 
when any two of the three factors are given. — Fig. 46. 



R = 



8V 



C = 2i/V(2Il — V) 



V=R->J- 



4R2 _ C2 



To find the length of any line perpendicular to the 
chord of an arc, when the distance of the line from the 
center of the chord, the radius of the arc and the length 
of the versed sine are given — Fig. 47. 




Fig. 47. 



N=i/(R2 _ X2)-.(R — H R = 



C2 + 4V2 

8V 



C = 2i/V(2R — V) 






I4R2 __ Q2 



32 MECHANICAL DRAWING 

To find the diameter of a circle when the chord and 
versed sine of the arc are given. 

^^ = ~GH 

To find the length of any arc of a circle, when the 
chord of the whole arc and the chord of half the arc are 
given — Pig. 48. 



Arc DHE == 



Fig. 



A Tangent is a straight line which touches the cir- 
cumference but does not intersect it. The point where 
the tangent touches the circle is called the Point of 
Tangency. 

Two Circumferences are tangent to each other when 
they are tangent to a straight line at the same point. 

A Secant is a straight line which intersects the cir- 
cumference in two points. 

A Polygon is inscribed in a circle w^hen all of its 
sides are chords of the circle. 

A Polygon is circumscribed about a circle when all 
of its sides are tangent to the circle, and a circle is 
circumscribed about a polygon when the circumference 
passes through all the vertices of the polygon. 



DEFINITION OF POLYGONS. 

A polygon, if its sides are equal, is called a regular 
polygon, if unequal, an irregular polygon. 
A pentagon is a five-sided figure. 
A hexagon is a six-sided figure— Fig. 49. 
A heptagon is a seven-sided figure. 
An octagon is an eight-sided figure. 



Fig. 49 — Hexagon. 

A nonagon is a nine-sided figure. 

A decagon is a ten-sided figure. 

A unadecagon is an eleven-sided figure. 

A duodecagon is a twelve-sided figure. 

GEOMETRICAL DEFINITION OF SOLIDS. 

A solid has length, breadth and thickness. The 
boundaries of a solid are surfaces. 

A solid angle is that which is made by two or more 
plane angles, which are not in the same plane, meeting 
at one point. 

33 



34 



MECHANICAL DRAWING 



A cube is a solid figure contained by six equal 
squares — Fig. 50. 

A prism is a solid figure contained by plane figures 
of which two that are opposite are equal, similar, and 
parallel to one another, the other sides are parallelo- 
grams — Fig. 51. 




Fig. 50 — Cube. 



Fig. 51 — Prism. 



A pyramid is a solid figure contained by planes, one 
of which is the base, and the remainder are triangles, 
whose vertices meet a point about the base, called the 
vertex or apex of the pyramid — Fig 52 





Fig. 52 — Pyramid 



Fig. 53 — Cylinder. 



A cylinder is a solid figure described by the revolu- 
tion of a rectangular or parallelogram about one of its 
sides — Fig. 53. 



GEOMETRICAL DEFINITIONS 



35 



The axis of a cylinder is the fixed straight line about 
which the parallelogram revolves. 

The ends of a cylinder are the circles described by 
the two revolving sides of the parallelogram. 

A sphere is a solid figure described by the revolution 
of a semicircle about its diameter, which remains 
fixed— Fig. 54. 

The axis of a sphere is the fixed straight line about 
which the semicircle revolves. 





Fig. 54 — Sphere. 



Fig. 55 — Cone. 



The center of a sphere is the same as that of the 
semicircle. 

The diameter of a sphere is any straight line which 
passes through the center and is terminated both ways 
by the surface of the sphere. 

A cone is a solid figure described by the revolution 
of a right-angled triangle about one of its sides con- 
taining the right angle, which side remains fixed — 
Fig. 55. 

The axis of a cone is the circle described by that side 
of the triangle containing the right angle which re- 
volves. 



36 MECHANICAL DRAWING 

The base of the cone is the circle described by that 
side of the triangle containing the right angle which 
revolves. 

If a cone be cut obliquely so as to preserve the base 
entirely, the section is an ellipse. 

When a cone is cut by a plane parallel to one of 
sloping sides, the section is a parabola^ if cut at right 
angles to its base, an hyperbola. 



MECHANICAL DRAWING. 

While many draftsmen are familiar with all of the 
problems given in this section of the work, it is not to 
be expected that all draftsmen or students are thor- 
oughly conversant with all of them, and it is intended 
that this section of the work shall be used not only as 
reference data but for practical examples of element- 
ary mechanical drawing. If the different problems 
given in this section are drawn with great accuracy, 
the technical skill acquired in drawing and proper 
handling of the different instruments will be found to 
be of great value. It will not be necessary to ink in 
these simple geometrical problems, as it is better to ac- 
quire precision or accuracy in pencil work before going 
further. These problems are believed to be an essen- 
tial part of a work on mechanical drawing. To under- 
stand geometry certain qualities of mind are absolutely 
necessary, and many persons find it impossible to grasp 
even the simple problems of this study. The drafts- 
man or student who is without practical knowledge of 
geometry is very poorly equipped for his duties. 



37 



GEOMETRICAL PROBLEMS. 

THE CONSTRUCTION OF ANGLES. 

To bisect a given angle. Let DAC be the given an- 
gle. With center A and any radius AE describe an arc 
cutting AC and AD at E and G. With the same radius 
and centers E and G, describe arcs intersecting at H, 
and join AH. The angle DAC is bisected — Fig. 56. 





Pig. 57. 

To construct an angle of 30°. With radius AE and 
with center A and E, describes arcs intersecting at G. 
With the same radius and with centers E and G, de- 
scribe arcs intersecting at D, and join AD. The angle 
DAC contains 30°— Fig. 57. 

To construct an angle of 60°. With radius AE, and 
with centers A and E, describe arcs intersecting at G, 
draw AD through G. The angle DAG contains 60° — 
Fig. 58. 

38 



GEOMETRICAL PROBLEMS 



39 



To construct an ang'le of 45°. With radius AE and 
centers A and E, describe arcs intersecting at F, draw 
EG through F, and make FG equal to FE. Join GR, 
and with center R and radius AE make AH equal to 





AE, with the same radius and with centers E and P 
describe arcs intersecting at L, draw AD through I* 
The angle DAC is 45°— Fig. 59. 




xF 



^^O 



1 



A EC 

Fig. 60. 

To construct an angle of 90°. With radius AE and 
centers A and E, describe arcs intersecting at F, with 
the same radius and center P describe the arc AGD, 
with radius AE^ lay off AG and GD and join DA. The 
angle DAG is 90°— Fig 60. 



40 



MECHANICAL DRAWING 



To bisect a straig-ht line — Fig 61. Let BC be the 

straight line to be bisected. With any convenient ra- 
dius greater than AB or AC describe arcs cutting each 
other at D and E. A ime drawn through D and E will 
bisect or divide the line BC into two equal parts. 



Fig. 61. 




Fig. 62. 



To erect a perpendicular line at or near the end of a 
straight line — Fig. 62. With any convenient radius 
and at any distance from the line AC, describe an arc 
of a circle as ACE, cutting the line at A and C. 




Through the center R of the circle draw the line ARE, 
cutting the arc at point E. A line drawn from C to E 
will be the required perpendicular. 

To divide a straight line into any number of equal 
parts—Fig. 63. Let AB be the straight line to be di- 



GEOMETRICAL PROBLEMS 



41 



vided into a certain number of equal parts : Prom the 
points A and B, draw two parallel lines AD and BC, 
at any convenient angle with the line AB. Upon AD 
and BC set off one less than the number of equal parts 
required, as A-1, 1-2, 2-D, etc. Join C-1, 2-2, 1-D, the 
line AB will then be divided into the required number 
of equal parts. 




To find the length of an arc of a circle — Fig. 64. Di- 
vide the chord AC of the arc into four equal parts as 
shown. With the radius AD equal to one-fourth of the 




Fig. 65. 

chord of the arc and with A as the center describe the 
arc DE. Draw the line EG and twice its length will 
be the length of the arc AEG. 

To draw radial lines from the circumference of a 
eircle when the center is inaccessible' — Fig. 65. Divide 



42 MECHANICAL DRAWING 

the circumference into any desired number of parts as 
AB, BC, CD, DE. Then with a radius greater than 
the length of one part, describe arcs cutting each other 
as A-2, C-2, B.3, D-3, etc., also B-1, D-5. Describe the 
end arcs A-1, E-S with a radius equal to B-2. Lines 
joining A-1, B-2, C-3, D-4 and E-5 will all be radial. 




To inscribe any regular polygon in a circle — Fig. 66. 

Divide the diameter AB of the circle into as many- 
equal parts as the polygon is to have sides. With the 
points A and B as centers and radius AB, describe arcs 
cutting each other at C. Draw the line CE through 
the second point of division of the diameter of AB, in- 
tersecting the circumference of the circle D. A line 
drawn from B to D is one of the sides of the polygon. 



GEOMETRICAL i^oi^LEMS 



43 



To cut a beam of the strongest shape from a circular 
section — Fig 67. Divide any diameter CB of the cir- 
cle into three equal parts as CF, FE and EB. At E 
and F erect perpendiculars EA and FD on opposite 
sides of the diameter CB. Join AB, BD, DC and CF. 
The rectangle ABCD will be the required shape of 
the beam. 




Pig. 67. 



To divide any triangle into two parts of equal area- 
Pig. 68. Let ABC be the given triangle : Bisect one 
of its sides AB at D and describe the semicircle AEB. 
At D erect the perpendicular DE and with center B 
and radius BE describe the arc EF which intersects 
the line AB at F. At F draw the line AG parallel at 
AC, this divides the triangle into two parts of equal 
area. 

To inscribe a circle of the greatest possible diameter 
in a given triangle — Fig. 69. Bisect the angles A and 
B, and draw th^^ lines, AD. BJD which intersect each 



44 



MECHANICAL DRAWING 



other at D. From D draw the line CD perpendicular 
to AB. Then CB will be the radius of the required 
circle CEF. 

To construct a square equal in area to a given circle 
— Fig. 70. Let ACBD be the given circle: Draw the 
diameters AB and CD at right angles to each other, 




Fig. 69. 



Fig. 70. 



then bisect the half diameter or radius DB at E and 
draw the line FL, parallel to BA. At the points C and 
F erect the perpendiculars CH and FG, equal in length 
to CF. Join HG, then CFGH is the required square. 
The dotted line FL is equal to one-fourth the circle 
ACBD. 



GEOMETRICAL PROBLEMS 



45 



To construct a rectangle of the greatest possible area 
in a given triangle — Fig. 71. Let ABC be the given 
triangle: Bisect the sides AB and BC at 6 and D. 
Draw the line GD and from the poirlts G and D, draw 
the lines GF and DE perpendicular to GD, then EFGD 
is the required rectangle. 




To construct a rectangle equal in area to a given 
triangle— Fig. 72. Let ABC be the given triangle: 
Bisect the base AB of the triano^le at D and erect the 




perpendiculars DE and BF at D and B. Through C 
draw the line ECF intersecting the perpendiculars DE 
and B at E and F. Then BDEF is the required rec- 
tangle. 



46 



MECHANICAL DRA^\'ING 



To construct a triangle equal in area to a given paral- 
lelogram— Fig". 73. Let ABCD be the given paral- 
lelogTani: Produce the line AB at B and make BE 
equal to AB. Join the points A and C and ACE will 

be the triangle required. 




To inscribe a square within a given circle — Fig. 74. 
Let ADBC be the given circle : Draw the diameters 
AB and CD at right angles to each other. Join AD. DB 
and CA. then ACBD is the inscribed square. 

E A F 




C 




H 



Fig. 



To describe a square without a given circle — Fig. 75. 

Draw the diameters AB and CD at right angles to each 
other. ThroiT^h A and B draw the lines EF and GH, 



GEOMETRICAL PROBLEMS 



47 



parallel to CD, also draw the lines EG and FH through 
the points C and D and parallel to AB, this completes 
the required square EFGH. 

To construct an octagon in a given square — Fig. 76. 
Let ABCD be the given square: Draw the diagonal 
lines AC and BD, which intersect each other at the 
point 0. With a radius equal to AO or OC, describe 
the arcs EF, GH, IK and LM. Connect the points EK, 
LG, FI and HM, then GFIHMKEL is the required 
octagon. 




Fig. 77. 



To construct a circle equal in area to two given cir- 
cles—Fig. 77. Let AB and AC equal the diameters of 
the given circles : Erect AC at A and at right angles 
to AB. Connect B and C, then bisect the line BC at D 
and describe the circle ACB which is the circle re- 
quired and is equal in area to the two given circles. 

To describe an octagon about a given circle — Fig, 
78. Let ACBD be the given circle : Draw the diame- 



48 



MECHANICAL DRAWING 



ters AB and CD at right angles to each other. With any 
convenient radius and centers A, C, B and D describe 
arcs intersecting each other at E, H, F and G. Join 
EP and GH which form two additional diameters. At 
the points AB and CD draw the lines KL, PR, MN and 
ST, parallel with the diameters CD and AB respect- 
ively. At the points of intersection of the circumfer- 
ence of the circle by the lines EF and GH, draw the 
lines KP, RM, NT and SL parallel with the lines EF 
and HG respectively, then PRMNTSLK is the required 
octagon. 




To draw a straight line equal in length to a given 
portion of the circmmference of a circle — Fig. 79. Let 
ACBD be the given circle: Draw the diameters AB 
and CD at right angles with each other. Divide the 
radius RB into four equal parts. Produce the diameter 
AB and B and make BE equal to three of the four 
parts of RB. At A draw the line AF parallel to CD 



GEOMETRICAL PROBLEMS 



49 



and then draw the line EOF which is to one-fourth of 
the circumference of the circle ACBD. If lines be 
drawn from E through points in the circumference of. 
the circle as 1 and 2, meeting the line AF and G and 
II, then C-1, 1-2 and 2-A will equal FG, GH and HA 
respectively. 




To construct a square equal in area to two given 
squares— Fig. 80. Let AC and AD be the length of the 
sides of the given squares: Make AD perpendicular 
to AC and connect DC, then DC is one of the sides of 
the square DCEG which is equal to the two given 
squares. 

To inscribe a hexagon in a given circle — Fig. 81. 
Draw a diameter of the circle as AB: With centers 
A and B and radius AC or BG, describe arcs cutting 



50 



MECHANICAL DRAWING 



the circumference of the circle at D, E, F and G. Join 
EF, FB, BG, GD, DA and AE, this gives the required 
hexagon. 




Fig. 81. 



To describe a cycloid^ the diameter of the generating* 
circle being given— Fig 82. Let BD be the generating 
circle : Draw the line ABC equal in length to the cir- 




cumference of the generating circle. Divide the cir- 
cumference of the generating circle into 12 parts as 
shown. Draw lines from the points of division 1, 2, 3, 
etc., of the circumference of the generating circle par- 



GEOMETRICAL PROBLEMS 



51 



allel to the line ABC and on both sides of the circle. 
Lay off one division of the generating circle on the 
lines 5 and 7, two divisions on the lines 4 and 8, three 
divisions on the lines 3 and 9, four divisions on the 
lines 2 and 10^ and five divisions on the lines 1 and 11. 
A line traced through the points thus obtained will be 
the cycloid curve required. 




To develop a spiral vnth uniform spacing — Pig. 83. 

Divide the line BE into as many equal parts as there 
are required turns in the spiral. Then subdivide one 
of these spaces into four equal parts. Produce the 
line BE to 4, making the extension E-4 equal to two 
of the subdivisions. At 1 draw the line 1-D, lay off 
1-2 equal to one of the subdivisions. At 2 draw 2-A 
perpendicular to 1-D and at 3 in 2-A draw 3-C, etc. 
With center 1 and radius 1-B describe the arc BD with 
center 2 and radius 2-D describe the arc DA, with cen- 
ter 3 and radius 3-A, etc., until the spiral is completed. 
If carefully laid out the spiral should terminate at E 
as shown in the drawing. 



MACHINE DRAWING 

The draftsman should not as a rule be content with 
simply reproducing the views shown in the different 
examples given, to the dimensions marked on them, 
but should lay out other views and cross sections. The 
great importance of the value of being able to make 
intelligible free hand sketches of machine details can- 
not be overestimated, the draftsman should practice 
this art, not only from the illustrations given herewith, 
but from actual machine details. Fully dimensioned 
free hand sketches of actual machines or their de- 
tails, form excellent examples for drawing practice. 
All such sketches should be made in a book kept for 
the purpose, always putting in the dimensions where 
possible. The description of the various applications 
of the mechanical powers hereinbefore given is more 
for reference than for the purpose of teaching these 
principles. As machine drawing is simply the appli- 
cation of the principles of geometry to the representa- 
tion of machines, if the draftsman or student is not 
already familiar with the study of geometry, he should 
make himself acquainted with the problems given in 
this work, before going further. 

U. S. Standard Hexagonal Bolt-head and Nut. Two 
types of head and nut are illustrated, the rounded 
or spherical, and the chamfered or conical, as shown 
in Fig. 84. Three dimensions are fixed by this stand- 
ard : First, the distance across the flats or short diam- 
eter, commonly indicated by H, and equal to one and 

52 



MACHINE DRAWING 



53 



one-half times the diameter of the bolt plus one-eighth 
of an inch; second, the thickness of the head, which 
is equal to one-half its short diameter; third, the 
thickness of the nut, which is equal to the diameter 
of the bolt. 





Fig. 84. Hexagonal-head Bolt and Nut. 



Example 1: Hexagonal head bolt and nut. Draw 

the views of the bolts and nuts as shown in Fig. 84, 
for bolts 4 inches long under head and 1 inch diame- 
ter. Scale — Full size. 



54 



MECHANICAL DRAWING 



Cast iron flange coupling. In the kind of coupling 
shown in Fig. 85 a cast iron center or boss provided 
with a flange is secured to the end of each shaft by 
a sunk key driven from the face of the flange. These 
flanges are then connected by bolts and nuts. 

To ensure the shaft being in line the end of one 
projects into the flange of the other. 




Fig. 85. Cast-iron Flange Coupling. 



In order that the face of each flange may be exactly 
perpendicular to the axis of the shaft they should 
be faced in the lathe, after being keyed on to the 
shaft. 

If the coupling is in an exposed position, where the 
nuts and bolt-heads would be liable to catch the clothes 
of w^orkmen or an idle driving band which might come 
in the way, the flanges should be made thicker, and 
be provided with recesses for the nuts and bolt-heads. 



MACHINE DEAWING 



55 



Dimensions op Cast-ikon Flange Couplings. 


Diameter 

of shaft 

D 


Diameter 

of flange 

F 


Thick- 
ness of 
flange 
T 


Diameter 

of boss 

B 


Depth 

at boss 

L 


Num- 
ber 
of 

bolts 


Diam- 
eter 
of bolts 
d 


Diameter 

of bolt 

circle 

C 


1% 


7X 


% 


3% 


2% 


3 


% 


5% 


2 


8% 


ItV 


4% 


3A 


4 


'% 


6% 


2% 


10% 


1% 


5A 


3% 


4 


X 


8% 


3 


12% 


ItV 


6% 


4A 


4 


1 


9% 


3X 


13% 


1% 


7% 


4% 


4 


1 


IOtV 


4 


14 


1% 


8 


5tV 


6 


1 


11% 


4>^ 


15% 


2 


8% 


6 


6 


1% 


12% 


5 


17% 


2% 


9if 


6% 


6 


IX 


13if 


5% 


18% 


2A 


10% 


7% 


6 


IM 


14% 


6 


19% 


2% 


11% 


7% 


6 


1% 


16 



The projection of the shaft p varies from i/4 iiich 
in the small shafts ':o % iii^h in the large ones. 

Example 2. Cast-iron Flange Coupling. Draw the 
views shown in Fig. 85 of a cast-iron flange coupling, 
for a shaft 5 inches in diameter, to the dimensions 
given in the above table. Scale — 3 inches to 1 foot. 

Proportions of Rivet Heads. The diameter of the 
snap head is about 1.7 times the diameter of the rivet, 
and its height about .6 of the diameter of the rivet. 
The conical head has a diameter twice and a height 
three-quarters of the rivet diameter. The greatest 
diameter of the oval head is about 1.6, and its height 
.7 of the rivet diameter. The greatest diameter of 
the countersunk head may be one and a half, and its 
depth a half of the diameter of the rivet. 

Example 3. Single-riveted butt Joints. In Fig. 86 
are shown two forms of single riveted butt joints. 



56 



MECHANICAL DRAWING 



Table Showing the Proportions op Single Eiveted 
Lap Joints for Various Thicknesses op Plates. 


Thickness of plates. 


A 


% 


7 
T"6- 


X 


9 


% 


1 1 


Diam. of rivets 
Pitch of rivets 


% 
lA 


Hi 


% 

2 


1 5 
T6" 

O 1 


1 

2i 


ItV 
2% 


21 



Distance from center of rivets to edge of plate = li^ times diameter 

of rivets. 




Fig. 86. Single Riveted Butt Joints. 

One of the sectional views shows a butt joint with one 
splice plate, the other sectional view shows a joint 



MACHINE DRAWING 



57 



with two splice plates. The plan view shows both 
arrangements. Draw all these views full size. 

Example 4. Corner of Wrought-iron Tajik. This 
exercise is to illustrate the connection of plates which 
are at right angles to one another by means of angle 
irons. Fig. 87 is a plan and elevation of the corner 
of a wrought-iron tank. The sides of the tank are 
riveted to a vertical angle iron, the cross section of 





Fig. 87. Corner of Wrought-iron Tank. 



which is clearly shown in the plan. Another angle 
iron of the same dimensions is used in the same way 
to connect the sides with the bottom. The sides do 
not come quite up to the corner of the vertical angle 
iron, excepting at the bottom where the horizontal 
angle iron comes in. At this point the vertical plates 
meet one another, and the edge formed is rounded 
over to fit the interior of the bend of the horizontal 
angle iron so as to make the joint tight. Draw this 
example half size. 



58 



MECHANICAL DRAWING 



The dimensions are as follows : angle irons 2^ 
inches X 2% inches X% inch, plates % inch thick, rivets 
% inch diameter and 2 inches pitch. 

Example 5. Gusset Stay. In order that the flat 
ends of a steam boiler may not be bulged out by the 




(3) 



KS\\ \\\\ ^ 



n^^\Wn\W s\ ^^ 




Fig. 88. Gusset Stays. 



pressure of the steam they are strengthened by means 
of stays. One form of boiler stay, called a gusset 
stay, is shown in Fig. 88. This stay consists of a 
strip of wrought-iron plate which passes in a diag- 
onal direction from the flat end of the boiler to the 



MACHINE DRAWING 



59 



cylindrical shell. One end of this plate is placed be- 
tween and riveted to two angle irons which are riv- 
eted to the shell of the boiler. A similar arrangement 
connects the other end of the stay plate to the flat 
end of the boiler. In this example the stay or gusset 
plate is % of an inch thick, the angle irons are 4 
inches broad and % inch thick. The rivets are 1 inch 
in diameter. The same figure also illustrates the most 




Fig. 89. Flanged Joint for Cast-iron Plates. 

common method of connecting the ends of a boiler to 
the shell. The end plates are flanged or bent over 
at right angles and riveted to the shell as shown. 
The radius of the inside curve at the angle of the 
flange is 11^4 inches. Draw this example to a scale of 
3 inches to 1 foot. 

Example 6. Flanged Joint for Cast-iron Plates. 
Draw the views shown in Fig. 89. Draw also a plan. 
The bolts and nuts must be shown in each view. The 



60 



MECHANICAL DEAWING 




MACHINE DRAWING Gl 

holes for the bolts are square, and the bolts have 
square necks. Draw this example half full size. 

Pillow Block. One form of pillow block is shown 
in Fig. 90. A is the block proper, B the sole-plate 
through which pass the holding down bolts. C is the 
cap. Between the block and the cap is the brass bush- 
ing which is in halves. 

In the block illustrated the journal is lubricated by 
a needle lubricator; this consists of an inverted glass 
bottle fitted with a wood stopper, through a hole in 
which passes a piece of wire, which has one end in 
the oil within the bottle and the other resting on the 
journal of the shaft. The wire or needle does not fill 
the hole in the stopper, but if the needle is kept from 
vibrating the oil does not escape owing to capillary 
attraction. When, however, the shaft rotates, the 
needle begins to vibrate, and the oil runs down slowly 
on to the journal; oil is therefore only used when the 
shaft is running. 

Example 7. Pillow Block for a Four-inch Shaft. 
Draw the views shown of this block in Fig. 90. Scale 
6 inches to 1 foot. 

Proportions of Pillow Blocks. The following rules 
may be used for proportioning pillow blocks for shafts 
up to 8 inches diameter. It should be remembered 
that the proportions used by different makers vary 
considerably, but the following rule»« represent average 
practice : 

Diameter of journal . . , = 6? 

Length of journal . , . . =Z 

Height to center .... =1.05^+ .5 

Length of base .... =3.6<^+5 



62 



MECHANICAL DRAWING 



Width of base 
block 
Thickness of base 

ii 

cap 
Diameter of bolts 



= .8l 

= ,1l 

= .25^+.25 



Distance between centers of cap bolts =1.6^+1.5 

base bolts =2.7^+4.2 
Thickness of step at bottom . . =t = 0^d-\-,\^ 

sides . . —%t 

The length of the journal varies very much in dif- 
ferent cases, and depends upon the speed of the shaft, 
the load which it carries, the w^orkmanship of the 
journal and bearing, and the method of lubrication. 
For ordinary shafting one rule is to make l=d-^l. 
Some makers use the rule 1=1. 5d, others make l=2d. 




K:^?)^ 



\^ 



Fig. 91. Sole Plate for a Pillow Block. 

Example 8. Sole Plate for a Pillow Block. Draw 

the view^s for a sole plate for a pillow block as showm 
in Fig. 91. Draw also an end elevation. Scale — ^Half 
size. 



MACHINE DRAWING 



63 



Example 9. Bracket for Pillow Block. Draw the 
side and end elevations shown in Fig. 92, and from 
the side elevation project a plan. Scale — Half size. 

Example 10. Wall Bracket and Bearing. Draw the 
side and end elevation partly in section as shown in 
Fig. 93, and project a complete plan below. Scale — 
Half size. 




Bracket for a Pillow Block. 



Pulleys. Let two pulleys A and B be connected by 
a belt, and let their diameters be D^ and D2; and let 
their speeds, in revolutions per minute, be N^ and N2 
respectively. If there is no slipping, the speeds of the 
rims of the pulleys will be the same as that of the belt, 
and will therefore be equal. Now the speed of the rim 
of A is evidently=DiX 3.1416 xNi, while the speed of 
the rim of B is=D2X 3.1416 XN^. Hence D^X 31416 
XNi=DiX 3.1416 XN2, and therefore 



64 



MECHANICAL DRAWING 



Pulleys for Flat Belts. In cross section the rim of 
a pulley for carrying a flat belt is generally curved 
as shown in Fig. 94, but very often the cross section 
is straight. The curved cross section of the rim tends 
to keep the belt from coming off as long as the pulley 
is rotating. Sometimes the rim of the pulley is pro- 
vided with flanges which keep the belt from falling 
off. 




-2^2" 







y I H ^■M-*'. 




M. 



1/ 7 "y'""^^^^ ^^^ 



Fig. 93. Wall-bracket and Bearing. 



Pulleys are generally made entirely of cast iron, but 
a great many pulleys are now made in which the cen- 
ter or hub only is of cast iron, the arms being wrought 
iron cast into the hub, while the rim is of sheet iron. 



MACHINE DRAWING 



65 



The arms of pulleys when made of wrought iron are 
invariably straight, but when made of cast iron they 
are very often curved. In Fig. 94, which shows an 
arrangement of two cast-iron pulleys, the arms are 
straight. Through unequal cooling, and therefore un- 
equal contraction of a cast-iron pulley in the mould, 
the arms are generally in a state of tension or com- 




Fig. 94. Tight and Loose Pulleys. 

pression, and if the arms are straight they are very 
unyielding, so that the result of this initial stress is 
often the breaking of an arm, or of the rim where 
it joins an arm. With the curved arm, however, its 
shape permits it to yield, and thus cause a diminution 
of the stress due to unequal contraction. 



66 MECHANICAL DRAWING 

The cross section of the arms of cast-iron pulleys is 
generally elliptical. 

Example 11. Tight and Loose Pulleys. Fig. 94 
shows an arrangement of tight and loose pulleys. A 
is the fast pulley, secured to the shaft C by a sunk 
key, B is the loose pulley, which turns freely upon 
the shaft. The loose pulley is prevented from coming 
off by a collar D, which is secured to the shaft by a 
tapered pin as shown. The nave or boss of the loose 
pulley is here fitted with a brass bushing, which may 
be removed when it becomes too much worn. Draw 
the elevations shown, completing the left-hand one. 
Scale 6 inches to 1 foot. 

By the above arrangement of pulleys a machine may 
be stopped or set in motion at pleasure. When the 
driving belt is on the loose pulley the machine is at 
rest, and when it is on the tight pulley the machine 
is in motion. The driving belt is shifted from the one 
pulley to the other by pressing on that side of the belt 
which is advancing towards the pulleys. 

Gear Wheels. Let two smooth rollers be placed in 
contact with their axes parallel, and let one of them 
rotate about its axis, then if there is no slipping the 
other roller will rotate in the opposite direction with 
the same surface velocity, and if D^, D2 be the diam- 
eters of the rollers, and N^, N2 their speeds in revolu- 
tions per minute, it follows as in belt gearing that 

If there be considerable resistance to the motion of 
the follower slipping may take place, and it may stop. 
To prevent this the rollers may be provided with teeth, 
then they become spur wheels, and if the teeth be so 



MACHINE DRAWING 67 

shaped that the ratio of the speeds of the toothed roll- 
ers at any instant is the same as that of the smooth 
rollers, the surfaces of the latter are called the pitch 
surfaces of the former. 

Pitch Circle. A section of the pitch surface of a 
toothed wheel by a plane perpendicular to its axis 
is a circle, and is called a pitch circle. We may also 
say that the pitch circle is the edge of the pitch sur- 
face. The pitch circle is generally traced on the side 
of a toothed wheel, and is rather nearer the points of 
the teeth than the roots. 

Pitch of Teeth. The distance from the center of 
one tooth to the center of the next, or from the front 
of one to the front of the next, measured at the pitch 
circle, is called the pitch of the teeth. If D be the 
diameter of the pitch circle of a wheel, n the number 
of teeth, and p the pitch of the teeth, then Dx 3.1416 
=nxp. 

By the diameter of a wheel is meant the diameter 
of its pitch circle. 

Form and Proportions of Teeth. The ordinary form 
of wheel teeth is shown in Fig. 95. The curves of the 
teeth should be cycloidal curves, although they are 
generally drawn in as arcs of circles. It does not fall 
within the scope of this work to discuss the correct 
forms of gear teeth. 

Example 12. Spur Gear. Fig. 95 shows the eleva- 
tion and sectional plan of a portion of a cast-iron spur 
gear. The diameter of the pitch circle is 23% inches, 
and the pitch of the teeth is 1% inches, so that there 
will be 50 teeth in the gear. The gear has six arms. 
Draw a complete elevation of the gear and a half sec- 
tional plan, also a half -plan without any section. Draw 



68 



MECHANICAL DRAWING 



also a cross section of one arm. Scale 3 inches to 1 
foot. 

Mortise Gears. "When two gears meshing together 
run at a high speed the teeth of one are made of wood. 
These teeth, or cogs, as they are generally called, have 
tenons formed on them, which fit into mortises in the 
rim of the gear. This gear with the wooden teeth 
is called a mortise gear. 




Fig. 95. Portion of a Cast-iron Spur Gear. 

Coupling Rods. A rod nsed to transmit the motion 
of one crank to another is called a coupling rod. A 
familiar example of the use of coupling rods will he 
found in the locomotive. Coupling rods are made of 



MACHINE DRAWING 



69 



wrought iron or steel, and are generally of rectangular 
section. The ends are now generally made solid and 
lined with solid brass bushes, without any adjustment 
for wear. This form of coupling rod end is found 
to answer very well in locomotive practice, where the 




Fig. 96. 



Locomotive Coupling-rod End. 



workmanship and arrangements for lubrication are ex- 
cellent. When the brass bush becomes worn it is re- 
placed by a new one. 

Fig. 96 shows an example of a locomotive coupling 
rod end for an outside cylinder engine. In this case 



70 MECHANICAL DEAWING 

it is desirable to have the crank-pin bearings for the 
coupling rods as short as possible, for a connecting 
rod and coupling rod in this kind of engine work side 
by side on the same crank-pin, which, being overhung, 
should be as short as convenient for the sake of 
strength. The requisite bearing surface is obtained 
by having a pin of large diameter. The brass bush 
is prevented from rotating by means of the square 
key shown. The oil-box is cut out of the solid, and 
has a wrought-iron cover slightly dovetailed at the 
edges. This cover fits into a check round the top 
inner edge of the box, which is originally parallel, 
but is made to close on the dovetailed edges of the 
cover by riveting. A hole in the center of this cover, 
which gives access to the oil-box, is fitted with a 
screwed-brass plug. The brass plug has a screwed hole 
in the center, through which oil may be introduced 
to the box. Dust is kept out of the oil-box by screw- 
ing into the hole in the brass plug a common cork. 
The oil is carried slowly but regularly from the oil-box 
over to the bearing by a piece of cotton wick. 

Example 13. Coupling Rod End. Draw first the 
side elevation and plan, each partly in section as shown 
in Fig. 96. Then instead of the view to the left, which 
is an end elevation partly in section, draw a complete 
end elevation looking to the right, and also a complete 
vertical cross section through the center of the bear- 
ing. Scale 6 inches to 1 foot. 

Stuffing-boxes. In Fig. 97 is shown a gland and 
stuffing-box for the piston rod of a vertical engine. 
A B is the piston rod, C D a portion of the cylinder 
cover, and E F the stuffing-box. Fitting into the bot- 
tom of the stuffing-box is a brass bush H. The space 



MACHINE DRAWING 



71 



K around the rod A B is filled with packing, of which 
there is a variety of kinds, the simplest being greased 
hempen rope. The packing is compressed by screwing 




Fig. 97. Gland and Stuffing-box. 

down the cast-iron gland L M, which is lined with a 
brass bush N. In this case the gland is screwed down 



72 



MECHANICAL DEAWING 




^-| M- 



Fig. 98. Water or Steam Cock, 



MACHINE DRAWING 



73 




74 



MECHANICAL DRAWING 



by means of three stud-bolts P, -which are screwed 
into a flange cast on the stuffing-box. Surrounding 







1 




t 






• • * 


^ — 


_ L _ 


- ^"- - - 


--^ 






1 
^ 1 

1 
1 

1 








r ' 

1 
1 
1 






1 










1 







Fig. 100. Details of Tail-stock. 



the rod on the top of the gland there is a recess R 
for holding the lubricant. 



MACHINE DRAWING 



75 



The object of the gland and stuffing-box is to allow 
the piston rod to move backwards and forwards freely 
without any leakage of steam. 

Example 14. Gland and Stuffing-box for a Vertical 
Kod. Draw the views shown in Fig. 97 to the dimen- 
sions given. Scale 6 inches to 1 foot. 







So ua Tc th Tea d.\ L eft h a nd. 
tti/e in reads her men. 






; -^ — M- 

'f I ^a (Aer iey ) 



'A^ 




^'1 



Fig. 101. Details of Tailstock. 

Water or Steam Cock. Fig. 98 shows a cock of con- 
siderable size, which may be used for water or steam 
under high pressure. The plug in this example is 
hollow, and is prevented from coming out by a cover 
which is secured to the casing by four stud bolts. 
An annular ridge of rectangular section projecting 
from the under side of the cover, and fitting into a 
corresponding recess on the top of the casing, serves 



76 



MECHANICAL DEAWING 



U 



m 



{\\\ \:\ \M 



^^ 



H ( D 



3 , , L 




^^ 




Fig, 102. Surface Gauge. 



MACHINE DRAWING 



'Ti 



to ensure that the cover and plug are concentric, and 
prevents leakage. Leakage at the neck of the plug 
is prevented by a gland and stuffing-box. The top 
end of the plug is made square to receive a handle for 
turning it. The size of a cock is taken from the bore 
of the pipe in which it is placed, thus Fig. 98 shows 
a 21/2-inch cock. 




Fig. 103. Details of Surface Gauge. 

Example 15. 2 1-2-inch Steam or Water Cock. First 
draw the views of this cock shown in Fig. 98, then 
draw a half end elevation and half cross section 
through the center of the plug. Scale 6 inches to 1 
foot. 

Instead of drawing the parts of the pipe on the 
two sides of the plug in the same straight line as in 
Fig. 98, one may be shown proceeding fr')m the bot- 



78 



MECHANICAL DRAWING 



torn of the casing^ so that the fluid will have to pass 
through the bottom of the plug and through one side. 
This is a common arrangement. 

All the parts of the valve and casmg in this ex- 
ample are made of brass. 




Fig. .104. Details of Surface Gauge. 

Example 16. Tailstock for 12-inch Lathe. Two 

views of this tailstock are shown in Fig. 99. On one 
of these views a few of the principal dimensions are 
marked. The details, fully dimensioned, are sho\vn sep- 
arately in Figs. 100 and 101. 

Explain clearly how the center is moved backwards 
and forwards, and also how the spindle containing it 
is locked when it is not required to move. 



MACHINE DRAWING 



79 



Draw, half-size, the views shown in Fig. 99, and 
from the left-hand view project a plan. Draw also 




Fig. 105. Jack Screw. 



the detail of the locking arrangement shown in Fig. 
100. 



80 



MECHANICAL DRAWING 



Example 17. Surface Gauge. First draw, full size, 
all the details separately, as shown in Figs. 103 and 
104, then draw, full size, the plan and two elevations 
of the tool complete, as shown in Fig. 102. 




HalJ seclioTiol Plcwi at AJB,. 

Fig. 106. Reversible Ratchet-drill. 



F is the scriber which may be clamped at any part 
of the straight portion, between D and E. The scriber 
may also be placed at any angle to the horizontal, 
and the point at which it is clamped may be placed 



MACHINE DRAWING 



Si 



at any height from the base A within the limits of 
the upright K. D and E are carried by the clamp H, 
which embraces the upright K. By turning the milled 



K-- 


- ^Ve - 


-->< 




A 


.. .± 




Fig. 107. Details of Ratchet-drill. 




;^ 



-^'oliam 



nut J the scriber is fixed in position in relation to K. 
A fine vertical adjustment is obtained by rotating the 
milled nut B. After all adjustments have been made^ 
K is locked in position by the set-screw C. 



£9 



MECHANICAL DBA WING 




Fig. 108. Steam Engine Governor. 

Example 18. Jack Screw. From the half elevation 
and half section shown in Fig. 105 make working 
drawings of the separate parts of the jack-screw, then 



MACHINE DRAWING 



83 



draw the views shown below of the complete machine. 
Scale 6 inches to 1 foot. 




K- zYz ^ 

Fig. 109. Details of Governor. 



Example 19. Reversible Ratchet-drill. Draw, full 
size, the views shown in Fig. 106 of a reversible ratchet- 



84 



MECHANICAL DRAWING 



brace. Draw also the details separately, as shown in 
Fig. 107. All the dimensions are to be obtained from 
the detailed drawings. 








u 




Fig. 110. Details of Governor. 



Example 20. Steam Engine Governor. Draw the 
half elevation and half section of the governor com- 



MACHINE DEAWING 



85 




^ 



Pi 









Fig. 111. Details of Governor. 



plete, as shown in Fig. 108. Draw also a plan and an 
elevation looking in the direction of the arrow (a). 
Scale 6 inches to a foot. All the dimensions are to 
be taken from the illustrations of the details shown 
in Figs. 109, 110, 111 and 112. 



86 



MECHANICAL DRiiWING 



The governor illustrated is used on an engine hav- 
ing a cylinder 8 inches in diameter, with a piston 
stroke of 16 inches. The crank-shaft runs at about 
110 revolutions per minute, and the governor-spindle 




^^^4^ 



-5^ holes 
Fig. 112. Details of Governor. 



^^ Hlj =A« H tW'rJfp 
fjln *-r-n rcUy "* 



is driven at three times the speed of the crank-shaft. 
The governor controls the expansion valve. This type 
of governor is known as the '^Porter'' governor, from 
the name of the inventor. 



MECHANICAL DRAWING AND MACHINE 
DESIGN. 

INDEX, 

PAGE 

Drafting tools i 

Compasses i 

Hair spring dividers 4 

Spring-bow instruments 5 

Ruling pens 6 

Sharpening a ruling pen 8 

Drafting instruments 9 

T-square 9 

Triangles or set-squares lo 

Testing triangles 11 

Scales II 

Curves 12 

Paper 13 

Pencils 14 

Pencil sharpeners 15 

Pencil erasers 15 

Ink erasers 16 

Eraser guard 16 

Drawing ink 16 

Protractor 18 

Drawing boards 18 

Thumb-tacks 19 

Lettering triangle 19 

Section liners 19 

i 



u INDEX 

PAGE 

Beam compasses 20 

Water colors 22 

Water color brushes 23 

Geometrical definitions of plane figures 24 

Definition of polygons 33 

Geometrical definition of solids 33 

Mechanical drawing 37 

Geometrical problems 38 

Construction of angles 38 

Machine drawing 52 




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